As Thai / Cambodia tensions hit new highs, do troop build-ups and nationalist rhetoric mean a hot conflict is on the horizon?

Key Takeaways:

• After a clash in the disputed border region of Preah Vihear in May 2025, tensions between Thailand and Cambodia have reached the highest level in years.

• A leaked phone call between Thai PM Paetongtarn Shinawatra and former Cambodian leader Hun Sen has initiated a political crisis in the country, culminating in her suspension and the potential collapse of the coalition government.

• While war remains unlikely, the buildup of troops and rising nationalist rhetoric on both sides give cause for concern.

• Fears are mounting that a military coup could be on the cards in Thailand, given the current political turmoil. The country’s history of successful coups and the army’s entrenched role in politics make this a credible risk.

While Thailand and Cambodia have had periods of peaceful coexistence, the relationship has also been marked by intermittent tensions, particularly concerning border disputes and historical grievances. The pair have undergone another escalation in tensions in recent weeks over a disputed border region. The matter is testing resolve on both sides, leading to escalating nationalist sentiment and a political crisis in Thailand that is still unfolding. Although a full conflict remains unlikely due to several factors making such a development attractive for both parties, the fallout from the current situation has sent shockwaves through the region.

Recent Events

On 28 May 2025, Thai and Cambodian patrols came across each other in the disputed region between Cambodia’s Preah Vihear province and Thailand’s Ubon Ratchathani province within the Emerald Triangle, where the borders of Cambodia, Thailand, and Laos meet. The two groups opened fire on each other, with the ensuing ten-minute skirmish resulting in the death of one Cambodian soldier. Both sides accused the other of firing first.

To try and ease tensions, Royal Thai Army Commander-in-Chief Pana Klaewplodthuk met with Commander of the Royal Cambodian Army General Mao Sophan on 29 May 2025. Their efforts would prove to be in vain. On 07 June 2025, Thailand confirmed that it had reinforced its military presence along the border, following an increase in troops on the other side. Things then deteriorated further as the two engaged in tit-for-tat measures. While Cambodia banned Thai films from TV and cinemas, cut internet bandwidth from Thailand, and suspended certain food and energy imports, Bangkok responded by closing border crossings into Cambodia to almost all travellers, including tourists and traders.

Then, in a strange twist, a phone call between Thai Prime Minister Paetongtarn Shinawatra and former Cambodian leader Hun Sen, was published in full by the latter after an initial clip was leaked, sparking a political crisis. The recording caused outrage in Thailand, with many accusing Shinawatra, who became the country’s youngest-ever Prime Minister in August 2024, of being too politically naive to protect the country’s national interests. She later issued an apology, stating that: "I had no intent to do it for my own interest. I only thought about how to avoid chaos, avoid fighting, and to avoid loss of lives”. As the political pressure continued to grow, the second-largest party in the ruling coalition, the Bhumjaithai Party, announced its withdrawal from the government on 18 June 2025. Ten days later, the people turned out in their masses on the streets of Bangkok to demand Shinawatra’s resignation. The protests were the largest seen since the ruling Pheu Thai party came to power in 2023.

On 01 July 2025, Thailand’s Constitutional Court voted by seven votes to two to suspend Shinawatra following a petition from 36 senators, who alleged dishonesty and a breach of ethical standards. The court is expected to take 45 to 60 days to reach a verdict from the day she was suspended. Another blow came on 14 July 2025, when the National Anti-Corruption Commission unanimously voted to set up a panel to investigate the suspended PM for ethical misconduct relating to the phone call. The development marked the beginning of a formal legal process, which could eventually result in charges and a referral of the case to the Supreme Court.

Even if the court reinstates Shinawatra, she will by no means be out of the political woods. With the coalition government’s fragile majority in the House of Representatives and growing economic challenges, such as sluggish investment, limited productivity growth, and US tariff concerns, mounting political challenges would be inevitable. Meanwhile, in the court of public opinion, her unpopularity is unlikely to go away anytime soon. According to a poll conducted by the National Institute of Development Administration (NIDA) between 19 and 25 June 2025, opposition leader of the People’s Party, Natthaphong Ruengpanyawut, was found to be the favoured candidate, with 31.48% of votes. While 19.88% of the sample said they did not see a suitable candidate, former PM General Prayut Chan-o-cha and Bhumjaithai Party Leader Anutin Charnvirakul received 12.72% and 9.64% respectively. Lastly, Shinawatra trailed behind with just 9.2%.

The Sinawatra political dynasty is no stranger to controversy. Former Leader Thaksin Shinawatra, who is also Paetongtarn’s father, was deposed following a military coup in September 2006 following accusations of corruption, abuse of power, and autocratic tendencies. He lived in exile for 15 years before returning in August 2023 and serving just six months of an eight-year sentence. He currently faces a hearing centred on allegations of royal defamation, an offence punishable by up to 15 years in prison. The verdict is scheduled for 22 August 2025.

In 2014, Paetongtarn’s aunt, Yingluck Shinawatra, was also removed as Prime Minister by the Constitutional Court after a ruling found her guilty of abusing her power when she transferred a senior civil servant to another position. In 2017, Yingluck was also found guilty of criminal negligence for her mishandling of a rice subsidy scheme, which allegedly cost Thailand at least $8 billion. She was sentenced in absentia to five years in prison and is believed to be living in London in exile.

Despite the political maelstrom unleashed in Thailand providing a distraction from the quarrel with Cambodia, bilateral tensions have failed to de-escalate. On 14 July 2025, Cambodian Prime Minister Hun Manet announced that his country would implement military conscription in 2026. The Military Conscription Law, which was approved in 2006 but never enforced, requires Cambodians aged 18 to 30 to serve for 24 months. Although both sexes can serve, doing so is voluntary for women.

Historical Origins

As with many of the world’s similar cases, the roots of this border dispute can be traced to the colonial era. As the European powers underwent their pursuits of global dominance, Siam, in what is present-day Thailand, found itself wedged between British India to the west and French Indochina to the east. As a consequence, Siam was forced to make a series of territorial concessions to avoid the fate of its neighbours. One agreement was the 1907 Franco-Siamese Treaty, which saw territories handed over to France and administratively attached to Cambodia. This included the area around Preah Vihear, a clifftop temple complex situated on the Dangrek mountain range.

During World War II, Thailand joined forces with imperial Japan and seized control of parts of western Cambodia. However, this didn’t last long as after Japan lost the war, France retook control of Indochina and Thailand was forced to return the occupied territories. When Cambodia regained independence from France in 1953, the colonial borders were left unchanged. Seeking to resolve the matter once and for all, Cambodia took the matter to the International Court of Justice, which ruled in 1962 that the temple was situated on Cambodian territory. As there was ambiguity concerning the sovereignty of the surrounding area, the court elaborated on its ruling in 2013, stating that Cambodia’s sovereignty also extended over the area around the temple. This made little difference to Bangkok, which has rejected the authority of the ICJ.

Things again became tense when Cambodia descended into a brutal civil war in the late 1960s. With the Khmer Rouge ascending to power from the ashes of a devastated Cambodia, the country’s new rulers oversaw a brutal reign under the leadership of Pol Pot from 1975 until 1979. Up to three million people were killed during the Cambodian genocide for failing to fall into the new regime’s vision of a homogenous, classless, agrarian utopia. After Vietnam overthrew the Khmer Rouge and occupied Cambodia, the border was transformed into a Cold War front line. With Vietnam under communist control and Thailand acting as a conduit for Western support to anti-Vietnamese resistance forces, the border experienced frequent clashes and fortification on both sides. Although Vietnam withdrew from the territory in 1989 as the Cold War drew to a close, the border has remained a sensitive matter.

Conclusion

Despite war appearing to be an unlikely outcome, the prospect has become more realistic than a few months ago. Considering Thailand’s overwhelming military strength relative to Cambodia, it is unsurprising that Phnom Penh would seek to avoid escalating the matter too far at the current time. Additionally, while there have been clashes over Preah Vihear before, a full-scale war has not broken out yet. Diplomatic ties had even warmed in recent years before recent events. Nevertheless, a resolution is by no means guaranteed. While the Association of Southeast Asia Nations was formed in part to prevent conflicts from arising among member states, the organisation lacks an effective dispute resolution mechanism. The raging civil war in Myanmar is a testament to this. Furthermore, with both sides going beyond rhetoric by increasing their troop presence in the area, the situation remains tense.

Even if the situation between the pair avoids further escalation, the chaotic domestic state of affairs in Thailand shows no signs of abating. With Thailand’s history of military coups, a weak civilian leader, and surging nationalism, the potential for the armed forces to step in is increasing. Even if the military doesn’t intervene, with Shinawatra’s Pheu Thai party under pressure from the opposition to call fresh elections or face a vote of no confidence, the political crisis is set to continue in her absence. While the government hasn’t ground to a deadlock just yet, it’s navigating a minefield of court cases, coalition fractures, and public unrest. The worst may be yet to come.