A Tangled Web on the Cambodia-Thailand Border

On May 28, Thai and Cambodian troops briefly exchanged gunfire on a disputed part of their border in the “Emerald Triangle,” a remote area where the borders of Thailand, Cambodia, and Laos converge. The clash left one Cambodian soldier dead. Trading blame for the firefight, Phnom Penh and Bangkok have since reinforced their military presence elsewhere along the shared border, while the diplomatic fallout has plunged relations to a decade-long low.

In the weeks following the clash, the Thai military restricted hours at 10 border checkpoints and Bangkok threatened to cut supplies of electricity and the internet to Cambodia. Phnom Penh responded by banning Thai television programs and movies, disconnecting cross-border internet links to Thailand, and ceasing imports of fruits, vegetables, and fuel.

Relations took another sharp dip on June 18, when Cambodia leaked a recording of a phone call between Thai Prime Minister Paetongtarn Shinawatra and Hun Sen, Cambodia’s influential former prime minister. In the call, the 38-year-old Thai leader referred to 72-year-old Hun Sen deferentially as “uncle” and accused the commander of Thailand’s Second Army Region of being “completely aligned with the other side” (i.e. her political opponents). The leak was met with an immediate backlash in Thailand.

With critics on right and left calling for her resignation, Bhumjaithai, the second-largest party in Paetongtarn’s governing coalition, withdrew its support, pushing the government to the brink of collapse. Paetongtarn survived the initial challenge, reshuffled her Cabinet, and adopted a tougher line on the border, but Bhumjaithai is planning to seek a no-confidence vote in July.

By late June, Thai officials were speaking of formally downgrading their relations with Cambodia.

It is no surprise that the two sides remain far apart on how to resolve the border issue. In mid-June, Cambodia wrote to the International Court of Justice (ICJ) in The Hague, asking it to rule on four disputed areas of the border: the Ta Moan Thom, Ta Moan Toch, and Ta Krabei temples, three Angkorian ruins that have been the subject of recent tensions, and the area close to the border with Laos, where the firefight took place on May 28. Prime Minister Hun Manet – Hun Sen’s son – has argued that only an independent party can resolve the border dispute “and extinguish it once and for all so that there is no further confusion.”

Thailand opposed intervention from the ICJ and made clear its preference for bilateral talks, including via the Joint Border Commission (JBC) that was set up in 2000 to adjudicate border disputes. The Thai Foreign Ministry has argued that “a third party may not always be conducive to the preservation of amicable relations among states, particularly in sensitive matters involving complex historical, territorial, or political dimensions.”

For decades, Cambodia and Thailand have sparred over their land border, which was set by treaties signed between Siam and French Indo-China in 1904 and 1907. However, despite the formation of the Mixed Delimitation Commission after the 1904 treaty, around a quarter of the border was never demarcated. In 2008, the two nations shed blood over Preah Vihear temple, an 11th-century Angkorian temple perched on a border clifftop, after UNESCO approved Cambodia’s application to add the temple on its World Heritage List. After several years of bilateral tensions and sporadic military clashes that displaced around 36,000 people, Phnom Penh took the case to the ICJ, which had awarded the temple to Cambodia in 1962. In 2013, the ICJ affirmed Cambodia’s sovereignty over the area, though the ruling is still contested in Thailand.

There are technical issues that make the Cambodia-Thailand border issue especially challenging, in particular the divergences in the cartographic methods that both nations have used to survey the border. But a bigger issue is the ardency of the nationalist sentiments that have been awakened by the conflict, and the extent to which these have become entangled in domestic politics, particularly in Thailand.

For both nations, the prospect of territorial loss is closely paired with feelings of humiliation, even of national erasure. Writing of Cambodia in 1991, Anthony Barnett observed that “in addition to pride in a unique greatness, most expressions of nationalism contain a fear of extinction.” While in many countries this fear is usually confined to the extremes of the political spectrum, he argued, “In the case of Cambodia it is central. There can be few countries where the theme has been accorded such weight.”

While most of the Cambodian anxiety has focused on Vietnam, disputes with Thailand have often had explosive real-world consequences. In early 2003, the Khmer-language press alleged that a Thai actress said that Cambodia had “stolen” Angkor Wat, and that she would not visit the country until it was “returned” to Thailand. Her alleged comments prompted thousands of protesters to sack and burn down the Thai Embassy and numerous Thai businesses in Phnom Penh, causing millions of dollars in damage. While the riots may have been inflamed by Hun Sen for his own political purposes, he was working with easily combustible materials. Similarly, Hun Sen benefited politically from UNESCO’s listing of Preah Vihear temple as a World Heritage Site in 2008, a “victory” that propelled his Cambodian People’s Party to a landslide election victory that year.

Thailand shares a similar anxiety about the integrity of its borders. Despite not being formally colonized by European powers – a point of pride to Thai nationalists – the Kingdom of Siam nonetheless experienced “continuous, sometimes violent confrontations with Western powers,” the historian Shane Strate wrote in his 2015 book “The Lost Territories: Thailand’s History of National Humiliation.” As Strate argued, the prideful claim that Thailand avoided colonization by the West comingles with a second, darker theme: one that “identifies the costs and consequences of survival, often portraying Siam as victim rather than victor.”

In Strate’s telling, this political narrative identifies and fixates on a series of “lost territories”: tracts of land that “once belonged to the Thai state but that were taken away by hostile powers through deceit or aggression.” This helps explain why Thai nationalists are so unnerved and apparently threatened by the actions of their objectively much weaker neighbor: behind Cambodia’s contemporary territorial claims lie the past humiliations at the hands of the French Empire.

More importantly, these claims have long had a considerable potency in Thai domestic politics, where they have been used as a weapon. “Lost territory is a tool for delegitimizing state leadership, as the government in question failed in its primary duty to secure the kingdom’s borders,” Strate wrote. “An effective way to discredit political opponents is to associate them with territorial loss.”

In this way, the current border dispute with Cambodia has been inflamed by Thai nationalists opposed to the influence of former Prime Minister Thaksin Shinawatra, Paetongtarn’s father, who returned to Thailand from self-exile in August 2023 and is widely viewed as the power behind his daughter’s government.

In attacking the Pheu Thai-led government’s border policies, many critics have focused on the close relationship between the Shinawatras and Cambodia’s Hun clan. This dates back nearly two decades. After Thaksin’s overthrow in a coup in 2006, Hun Sen provided refuge to him in Cambodia and even named him an honorary economic adviser during the tensions over Preah Vihear. Hun Sen has also opened the doors of his Phnom Penh mansion to Thaksin’s sister, Yingluck, who was overthrown in another coup in 2014 and remains in self-exile abroad.

Now that their children are in power, Thai critics say, the warm relationship between Thaksin and Hun Sen has prevented Paetongtarn’s government from doing what is necessary to defend Thai sovereignty. These arguments were seemingly validated by the leak last month of the recorded call between Paetongtarn and Hun Sen, in which the Thai leader effectively positioned herself with Hun Sen against the Thai military – an institution that has historically depicted itself as the final guardian of Thailand’s sovereignty and territorial integrity.

For all of these reasons, an immediate solution to the border crisis appears a long way off. It could also have unpredictable political reverberations in Thailand. The 2006 and 2014 coups, which overthrew Shinawatra-led  governments, were both preceded by border tensions with Cambodia that political enemies used to undermine the government’s legitimacy and justify a military intervention.

The Cambodian government has less to worry about, having exiled or arrested most of its domestic political opponents. But Cambodian exiles have accused it of failing to defend Cambodian national interests, particularly the country’s claim over the island of Koh Kood in the Gulf of Thailand, and Hun Manet’s administration could still pay a political price if it is seen to capitulate to Thai demands.

Cambodia’s government is right that legal mediation is probably the only path toward a permanent solution, but whether Phnom Penh is genuinely interested in this remains uncertain. It is similarly unclear whether either nation could politically accept an ICJ ruling, if it went against them. Now that nationalist sentiments are engaged, neither government has much room for maneuver. About the best that can be expected is a slow mutual de-escalation toward the status quo ante, leaving the border issue primed once against to erupt.