Border Dispute with Cambodia Sparks Political Disarray in Thailand

Thailand’s Constitutional Court suspended Prime Minister Paetongtarn Shinawatra from office on 1 July, as the political fallout from a rancorous border dispute between Thailand and Cambodia spreads, above all in Bangkok. The court suspended Paetongtarn after taking up a petition submitted by 36 senators, who argued that she had committed ethical violations breaching the country’s constitution in a 15 June phone call with former Cambodian prime minister Hun Sen, which was leaked three days later. The timing and nature of the call were charged with political significance, coming amid a precipitous downturn in bilateral relations sparked by a 28 May clash between Cambodian and Thai troops along an undemarcated stretch of the border, in which a Cambodian soldier was killed. In the fateful phone call, Paetongtarn denigrated the Second Army Region commander responsible for Thailand’s north east and adopted a deferential tone with Hun Sen, who remains extremely influential despite having passed the premiership on to his son, Hun Manet, in 2023. The leaked call has become a bombshell, rocking the coalition government led by Paetongtarn’s Pheu Thai Party and fuelling nationalist criticism that she has betrayed her country.

Tensions between the two South East Asian neighbours have soared, meanwhile, with each side sending more troops to the border amid volleys of bellicose rhetoric following the skirmish in May. On 23 June, after both sides instituted a series of tit-for-tat border restrictions, the Thai army closed all border crossings until further notice.

Now serving as president of Cambodia’s Senate, Hun Sen has heaped blame on Bangkok for stoking the ill-will and ridiculed the Thai government for being unable to control its military. He has antagonised the Thai government with a series of statements and Facebook posts, including one in which he declared that Paetongtarn would no longer be prime minister in three months’ time, adding that he knew who would replace her. Hun Sen denied leaking the call at the heart of the scandal, but subsequent events leave no doubt that he has decided to end a decades-long professional and personal association with former Thai Prime Minister Thaksin Shinawatra, Paetongtarn’s father, whom he once called his “godbrother”. Speaking on 26 June, he warned Thaksin that, “If you act arrogantly, I will expose everything you told me, including your insults to your king”. 

Paetongtarn has been given until 15 July by the Thai Constitutional Court to submit a written defence. If the court finds the charges against her to be valid, she will be disqualified from holding office. Deputy Prime Minister Suriya Jungrungreangkit is now acting prime minister.

Tensions along the land border have been simmering since early in the year, culminating in the 28 May skirmish. In February, Cambodian troops and civilians climbed to the ruins of a disputed Khmer Empire-era temple, Prasat Ta Muen Thom, and sang a patriotic song. They were confronted by Thai troops, who objected to the implicit assertion of Cambodian sovereignty. A video of the confrontation circulated on social media, fanning nationalist sentiment in both countries. Attention then shifted to the Emerald Triangle, where Cambodia, Laos and Thailand meet, after a pavilion commemorating the tri-border area burned down on 1 May. Thai officials sought to quash rumours that Cambodian troops had started the fire, stating publicly that the origins of the blaze were innocent. In mid-May, the Thai army reported that Cambodian troops were digging trenches in disputed territory, but that they had agreed to withdraw after discussions between local commanders. The deadly clash took place shortly thereafter in the same area, known in Thailand as Chong Bok and in Cambodia as Mom Bei.

Cambodia has taken the matter to the International Court of Justice (ICJ), seeking a ruling on disputed territory in four areas along the frontier where the border is not clearly defined. But Thailand rejects the ICJ’s jurisdiction on this issue, insisting that the territorial disputes be resolved bilaterally through a Joint Boundary Commission under terms agreed upon in a 2000 memorandum of understanding.

These incidents are the latest in a history of conflict along the 817km land border between the two South East Asian nations, portions of which are subject to overlapping territorial claims due to disagreements about colonial-era maps. The last major clashes occurred between 2008 and 2011, when fighting and artillery exchanges killed at least 34 people, wounded many more and displaced thousands. 

At that time, the locus of tension was sovereignty over the ancient Hindu temple of Prasat Preah Vihear, built between the 9^th to 11^th centuries AD by the Khmer Empire, which sits on a promontory in the Dangrek mountain range that broadly forms the frontier between the two countries. Tensions around this temple were not new: in 1959, Cambodia called on the ICJ to determine which country owned the famed monument. In 1962, the court ruled that the temple is situated in Cambodia, reasoning that the kingdom of Siam, and later Thailand, had earlier accepted a 1907 map drafted by French officials that put it in Cambodian territory. Thailand accepted the ruling, but bitterness over the legal defeat revived a narrative of territory lost to colonial powers. 

Thai nationalists have since nurtured irredentist hopes of reclaiming the temple. In November 2013, the ICJ confirmed its original decision that the temple is situated in Cambodian territory. But the court maintained that it has no jurisdiction to determine a boundary line on disputed land in the temple’s vicinity, allowing both sides to claim victory.

At the popular level, social media has amplified these anachronistic disputes in both countries over the “true” ownership of shared heritage, from Khmer Empire temples to traditional dance and martial arts. Even before these arguments proliferated online, a mob in Phnom Penh looted and burned the Thai embassy in 2003, angered by comments falsely attributed to a Thai actress that Angkor Wat, the Khmer architectural wonder and cultural icon of Cambodia, rightfully belongs to Thailand.

Even before the latest border crisis, the Pheu Thai-led coalition government was facing strong political headwinds and dwindling popularity, having failed to fulfil signature campaign promises and struggled to revive the economy. The coalition was born of a Faustian bargain between Thaksin and his former antagonists in the conservative establishment – an unnatural alliance designed to prevent the upstart and progressive Move Forward Party from forming a government after its surprise 2023 election victory. The deal thrust Pheu Thai into league with political factions that have regarded Thaksin as their nemesis since before his ouster in a 2006 coup. Rifts in the coalition were nearing the breaking point when the leaked call went viral, leading Interior Minister Anutin Charnvirakul to resign on the same day and take his Bhumjaithai Party, the second largest party in the coalition, into opposition. 

Against this backdrop, the scandal over the call has proven enormously damaging to Prime Minister Paetongtarn, highlighting the open secret of distrust between Pheu Thai and the military. Paetongtarn had earlier been at pains to dismiss rumours of discord between her government and the army, which has staged twelve successful coups since 1932. Perhaps most damaging is that the call appears to many Thais to buttress the longstanding accusations of Thaksin’s opponents that the Shinawatra clan is eager to “sell the country” for private gain. 

In the immediate aftermath of the leak, Paetongtarn weathered demands that she resign and dissolve parliament. But the Bhumjaithai Party’s exit from the coalition left the government with only a slender majority. Paetongtarn apologised to the public for the leaked call, excusing her ingratiating tone as a negotiating tactic. She also visited troops on the border and publicly mended fences with Lieutenant General Boonsin Padklang, the Second Army Region commander, who told reporters he had “no problem” with her comments about him in the call. The Pheu Thai Party has in turn rallied the remaining coalition partners, suggesting that important conservative constituencies, some of which have close links to the military, presently see no better alternative to the alliance of convenience with Thaksin. In the pending cabinet reshuffle, currently awaiting royal endorsement, Pheu Thai will surrender the defence portfolio to a retired general. 

Besides showing contrition and shoring up the coalition, Paetongtarn had also gone on the offensive against Cambodia, highlighting the country’s role in hosting cyber-scam centres and as a money laundering hub. On 19 June, Thailand’s Deputy Prime Minister and Digital Economy Minister Prasert Jantararuangtong held a press conference on transnational cyber fraud stating that the “world is watching” Cambodia’s emergence as an alleged centre of scam operations. According to the U.S. Institute of Peace, Cambodia’s scam centres may generate as much as $12.5 billion annually, roughly half the country’s formal gross domestic product. Another recent report argues that “Cambodian state institutions systematically and insidiously support and protect the criminal networks involved in transnational fraud and related human trafficking”. Paetongtarn chaired a meeting of senior officials to address transnational organised crime on 21 June, after which she told reporters that she would invite other countries to join with Thailand in combating Cambodia’s scam centres. Calling this campaign a “national priority”, Paetongtarn demanded “a tangible drop in complaints … and a rise in prosecutions” within three months. 

As part of the crackdown on call centre scams and online fraud, the Thai authorities are also stepping up investigations of cyber fraud and criminal financial transactions, tightening border security, and halting exports of fuel and electricity that might support scam centres. 

Despite her efforts, Paetongtarn’s position is increasingly precarious. Now that she has been suspended for the duration of the Constitutional Court’s investigation, long-time Thaksin adversaries will not wish to squander the opportunity to oust his daughter and finally shatter his political sway. Since Thaksin was toppled in a coup in 2006, the Constitutional Court has disqualified all four of his subsequent proxy prime ministers (twice in 2008, then 2011 and 2024). Other petitions requesting investigations into alleged criminal and ethical violations are also working their way through the National Anti-Corruption Commission and the Election Commission; they could result in Paetongtarn’s disqualification from holding office. Meanwhile, the Bhumjaithai Party said it will file a no-confidence motion against the prime minister when parliament reopens on 3 July. Some are concerned that anti-government protests will pave the way for another coup. 

The border has long been a thorn in bilateral relations, but it appears that the current crisis echoes earlier episodes in that it largely stems from domestic political interests fanning the dispute on both sides. 

Territorial disagreements have become entwined with Thailand’s bitter political divides due to the longstanding relationship between Thaksin and Hun Sen. Thaksin took refuge in Cambodia while in exile following the 2006 coup that deposed him, as did his sister, former Prime Minister Yingluck Shinawatra, after the 2014 coup. In 2009, at a time of heightened tensions between the two countries, Hun Sen appointed Thaksin as an adviser, a move designed to provoke the Thai establishment. When Thaksin was released on parole in 2024 by the Thai authorities after being convicted of abusing power, Hun Sen immediately paid him a personal visit in Bangkok.

Thai nationalists have in turn exploited the close relationship between the two strongmen as a rallying cry. They deployed this friendship as a running theme in mass protests in 2008 that destabilised the government at the time, which was aligned with Thaksin. Cambodia had sought, with Thailand’s support, to have the Preah Vihear temple inscribed in the World Heritage list maintained by the UN Education, Scientific and Cultural Organisation, or UNESCO. But protesters accused the ex-prime minister of nefarious, self-interested dealings with Hun Sen that posed a threat to the fundaments of Thailand’s sovereignty. 

Since Paetongtarn became prime minister in 2024, nationalist critics have continued to focus their fire on the Shinawatras’ alleged perfidy. Before the border dispute resurfaced, they had drawn attention to overlapping maritime claims between the two countries, calling for Thailand to withdraw from a 2001 memorandum of understanding that provides a framework for negotiations on maritime demarcation and joint development of energy resources. These critics alleged that the memorandum, negotiated when Thaksin was prime minister, put the country at risk of losing sovereignty over Koh Kut, an island in the Gulf of Thailand. As tensions erupted over the land border, Thaksin’s adversaries again used panic about losing territory to Cambodia as a cudgel against the Pheu Thai government. 

From the Cambodian side, Hun Sen and Hun Manet appear to be relishing their daily rhetorical broadsides against Bangkok. For the moment, Cambodia’s leaders appear to be chasing a wave of Khmer nationalism. Traditionally, rallying calls around the flag have been a tool of the opposition to Hun Sen’s Cambodian People’s Party (CPP). Hun Sen methodically and comprehensively crushed this opposition following a strong showing by the rival Cambodian National Rescue Party (CRNP) in the 2013 election. Cambodia’s Supreme Court eventually dissolved the CNRP in 2017 for conspiring with foreign powers to topple the CPP-led government. Opposition politicians have been jailed, driven into exile and murdered. One such exiled politician, Lim Kimya, was shot to death in Bangkok in January. 

At the same time, the Cambodian government and courts have eviscerated independent media and cowed non-governmental organisations. Facing severe economic problems and with no internal opposition to serve as a foil, Hun Sen may derive some benefit from a nationalistic surge to rally support and stifle factionalism within the CPP. 

Meanwhile, observers are left to speculate about why Hun Sen has chosen this moment to burn his bridges with Thaksin. Among the various theories being expounded, some suggest that Hun Sen was concerned about a Thai crackdown on transnational crime amid mounting evidence of Cambodian elite complicity in cyber-scam centres. 

The swift deterioration of security along the border is an indictment of the two countries’ failure to resolve their rival claims since the last round of fighting in 2011. Delimitation of the border and a lasting resolution awaits a less heated bilateral relationship. But Cambodia’s decision to seek a ruling from the ICJ is unlikely to resolve the matter of the four disputed sites at the centre of the current tensions, given that Thailand rejects the court’s jurisdiction. Even if the ICJ decides to intervene, Bangkok would not acknowledge an adverse ruling, meaning that an actual resolution of the dispute would still require negotiation and agreement between the two sides. Meanwhile, daily provocations from Phnom Penh leave Paetongtarn little scope for conciliatory moves as she seeks to fend off domestic political attacks for her supposed subservience to Cambodia.

Both countries and their respective political leaderships stand to lose from a prolonged crisis. Border trade amounted to more than $5 billion in 2024, with Thailand running a $3 billion surplus. Effects of a prolonged border closure will be felt most strongly by local people on both sides whose livelihoods depend on cross-border commerce that has ground to a halt. Thailand records some 500,000 Cambodian migrant workers in the country, but Cambodian government data indicate the number could in fact be twice as high. Hun Sen and Hun Manet have urged Cambodians in Thailand to return home, raising the spectre of expulsion and pledging government assistance and jobs to returnees. Thai authorities, however, insist they will not expel Cambodian workers, who are vital to agriculture and construction in parts of Thailand. 

As members of the Association of South East Asian Nations (ASEAN), Cambodia and Thailand are obliged by the Treaty of Amity and Cooperation to settle disputes between member states peacefully. In 2008, ASEAN’s then-chair, Indonesia, attempted to play a mediating role but was frustrated by the precedence the parties gave to the principle of non-interference in internal affairs. ASEAN’s current chair, Malaysia, has not sought to intervene in the standoff, and there appears to be no interest on either side in mediation from the regional body or another third party.

Bilateral negotiations, for which mechanisms already exist, should offer a more reliable means of finding a compromise. Under the terms of a 2000 memorandum of understanding, the Joint Boundary Commission is responsible for jointly surveying and demarcating the land boundary. The commission, which is meant to convene at least once a year but had not done so since 2012, met in Phnom Penh on 14-15 June, but Cambodia insisted that it would not discuss the four disputed areas that feature in its submission to the ICJ. The body, has however, scheduled a special meeting for September. 

Beyond making full use of this commission, the two sides need to avail themselves of every opportunity to lower the temperature and avoid misunderstandings. The General Border Committee, established in 1995 for ministerial-level exchanges on border security, and the Regional Border Committee, to facilitate discussions between local-level military commanders, should convene as often as necessary. A meeting of the Region Border Committee scheduled for 27-28 June was cancelled.

For now, it is imperative that both sides refrain from escalatory moves or deployments that risk unplanned military encounters. The risks of further fighting, which would harm both sides, are apparent and should impel decision-makers to restore the border to the status quo ante. The disputed areas are small and inconsequential except as totems of the sacred homeland in the respective countries’ nationalist imagination. Miscalculation or provocation could all too easily lead to deepening economic hardship and further loss of life.