EXPLAINER – Why are Thailand and Cambodia fighting over their border?

Cambodian and Thai forces clashed along their disputed border on Thursday, with Thailand deploying F-16 fighter jets and Cambodia firing rockets, killing at least 12 people and injuring 17, according to Thai authorities. The escalation was triggered by landmines laid along the border.

Where is the disputed border?

The two neighbours contest parts of the border stretching across Cambodia’s Preah Vihear province and Thailand’s northeastern Ubon Ratchathani province.

Tensions have been rising since 28 May, when a Cambodian soldier was killed in what was described as cross-border fire.

How did this dispute begin?

Cambodia’s claim is based on a 1907 map created during French colonial rule under the Franco-Siamese treaty, which placed areas such as the Preah Vihear Temple under Cambodian control, according to Modern Diplomacy.

Thailand has long contested this, arguing the map was unilaterally drawn by French officials without Thai consent and deviated from natural watershed boundaries, creating conflicting interpretations.

Efforts to resolve the issue diplomatically failed. 

The International Court of Justice (ICJ) ruled in 1962 that the Preah Vihear Temple belonged to Cambodia, but other parts of the border remained undefined, keeping tensions alive.

A further ICJ ruling in 2013 confirmed Cambodia’s sovereignty over the surrounding promontory but left adjacent disputed areas unsettled.

Why did fighting erupt in the past?

The dispute turned violent in 2008, shortly after the Preah Vihear Temple was listed as a UNESCO World Heritage site, which Thailand opposed. 

Both sides accused each other of starting the fighting.

The most deadly clashes were in 2011, killing at least 15 people and displacing tens of thousands.

Fighting centred on jungle border areas dotted with ancient temples claimed by both sides.

A cease-fire was declared after seven days, but sporadic skirmishes continued as the border remains undemarcated.

Why are landmines making things worse?

Cambodia remains one of the world’s most heavily mined countries, with an estimated 4–6 million landmines and unexploded ordnance (UXO) left from decades of conflict, including the Khmer Rouge era and the Vietnam War, according to APOPO.

The high density of mines has made border regions dangerous, contributing to one of the highest amputee rates per capita globally.

Demining efforts by organizations such as The HALO Trust and the Cambodian Mine Action Centre (CMAC) have cleared over 500 million square metres of land, but vast areas remain contaminated, increasing the risk of accidental cross-border incidents.

What has the UN and ICJ done?

In 1962, the International Court of Justice (ICJ) ruled that the Preah Vihear Temple belongs to Cambodia. However, the decision did not fully settle the dispute as the surrounding areas remained undefined.

In 2011, the United Nations ordered both sides to withdraw their forces and establish a demilitarized zone around the disputed area. 

However, the UN did not decide who would control the larger territories where clashes continued to occur.

In November 2013, the ICJ confirmed Cambodia’s sovereignty over the entire Preah Vihear temple complex and ruled that Thailand was obligated to withdraw its military personnel from the area. 

Despite this, tensions have persisted due to unresolved claims over other border regions.

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News Thailand Cambodia Border dispute Politics Thai-Cambodian clashes Southeast Asia border tensions Colonial-era border dispute Thailand Cambodia military escalation