This dyad belongs to the conflict Cambodia (Kampuchea) - Thailand

Summary of conflict Cambodia (Kampuchea) - Thailand

The border conflict between Cambodia and Thailand dates back to 1954 when both countries claimed sovereignty over the Temple of Preah Vihear. The fighting escalated in 1977-1978 with clashes at several different locations along the border. However, during 1978, tensions inside Cambodia and along the Cambodian-Vietnamese border grew, which eventually lead to a cessation of the fighting along the Thai border. The Temple dispute remained unsolved and caused new tensions in 2008 and 2009. In 2011 violence reached the level of armed conflict, but subsided quickly.

2025

In 2025, the conflict between Thailand and Cambodia, which had been inactive for several years, flared up once more. The first fatality occurred in May, when a Cambodian soldier was shot at the Cambodian-Thai border. This resulted in increased tension between the countries, and in late July clashes broke out and quickly escalated. Aside from military losses, civilians were also heavily affected, as 23 civilians were killed during the clashes and widespread displacement occurred along the border provinces. A ceasefire was implemented after a few days, and hostilities ended. In October, the Kuala Lumpur Peace Accord was signed with the purpose of ensuring the implementation of the ceasefire, normalizing the relations, and ensuring the commitment to solving border disputes through peaceful means. Still, clashes broke out once more in December and lasted for almost three weeks. On December 27th, a new ceasefire agreement was put in effect and clashes halted.

Background to the conflict

The border conflict between Cambodia and Thailand was to a large extent caused by the use of different maps and poor border demarcations. Cambodia used a map from 1909, produced by a Franco-Cambodian commission following agreements between France and Thailand in 1904 and 1907. Thailand on the other hand used an American military map from 1954. The battle-front shifted throughout the conflict and clashes occurred along the whole border. One reason for this was reportedly that several of the border demarcations were kilometers apart which caused uncertainty about the location of the actual borderline. It should also be noted that Thailand had previously, in 1941, occupied the two Cambodian provinces that saw the most intense fighting, Battambang and Sisophon. Thailand was later forced, under the “Treaty of Washington”, to return the two provinces to Cambodia in 1946. The disputed area that received the most regional as well as international attention was however the ancient Temple of Preah Vihear, located at the northern Cambodian-Thai border.

The Temple of Preah Vihear and the ICJ ruling in 1962

In October 1953, France yielded to Cambodia’s demand for independence and the formal transfer of power took place on 9 November 1953. Cambodia’s status as an independent country was formally recognized at a conference in Geneva in 1954. Following the French withdrawal, Thailand set up a police station just north of the Temple of Preah Vihear located at the northern border between Cambodia and Thailand. The Thai flag was also hoisted over the ancient sanctuary. Cambodia immediately claimed to have sovereign right over the Temple and negotiations between the two parties were held between 1954 and 1958. No agreement was reached during these years and in 1959 Cambodia filed proceedings at the ICJ (International Court of Justice). Cambodia asked the Court to declare Thailand obliged to withdraw its troops which, according to Cambodia, had been stationed there since 1954.

In 1962, the Court ruled in favor of Cambodia arguing that Thailand had accepted the terms of the agreement from 1904 and had adhered to it for more than 50 years. Maps produced following the agreement, maps which Thailand had used, placed the Temple in Cambodia. Thailand objected to the decision but withdrew from the Temple later the same year. The Thai flagpole that was raised in 1954 was removed in a standing position and placed in a Thai museum, which was interpreted by some as an indication of Thailand’s continued claim to the Temple.

There is little reliable information regarding the following years and the intensity of the border dispute. The dispute also came to include several other locations such as the Ko Kut (Koh Kong) Island and the border area neighboring the Cambodian provinces Battambang and Sisophon. The earliest recorded armed violence related to the border dispute occurred in June 1965 when Cambodian and Thai forces allegedly clashed in heavy fighting. It is, however, possible that armed violence was used earlier than June 1965.

The fighting escalates under the Khmer Rouge 1975-1978

The border dispute between Cambodia and Thailand intensified after the Khmer Rouge forcibly had taken power in Cambodia in 1975 (the country was subsequently renamed Kampuchea). A number of clashes between Kampuchean and Thai forces took place during 1975 with several fatalities reported. Despite some conciliatory steps in 1976, the fighting escalated in 1977. Clashes were reported at a number of locations along the border, but the most notable ones took place in the Prachinburi province in Thailand, located east of Bangkok.

The Kampuchean authorities claimed that the Thai military was supporting Kampuchean rebels operating along the border, named “Free Khmers”. This was denied by the Thai authorities which in turn reported several Kampuchean attacks on Thai villages close to the border.

Negotiations were held between the two countries on 30 January – 2 February 1977 when a Thai delegation visited the Kampuchean capital Phnom Penh. The outcome of the visit was an agreement to implement the joint communiqué that had been drafted on 31 October 1975. The communiqué aimed to normalise relations, resume economic and trade relations and establish diplomatic relations in terms of exchanging ambassadors. Despite the agreement, the relations between Kampuchea and Thailand remained tense throughout 1978, with repeated clashes during mainly the first half of the year.

During the second half of 1978, the Kampuchean regime faced an increased threat from Vietnam and in December the fighting escalated along the Kampuchean-Vietnamese border. The Kampuchean regime’s focus shifted from the Thai border to the Vietnamese border and the border clashes with Thailand eventually ceased. The question of the exact location of the border between Kampuchea and Thailand was, however, not solved. The fighting along the Kampuchean-Thai border continued during the following years, but was then related to the conflict over governmental power in Cambodia.

New tensions regarding the Temple of Preah Vihear in 2008-2009

Although the armed border conflict between Cambodia (Kampuchea was renamed Cambodia in 1989) and Thailand eventually lapsed, the dispute over the Temple of Preah Vihear remained. One example of this can be found in maps produced by Thailand in the 1990s which clearly put the Temple within its territory. Furthermore, the question was put on the agenda once again when Cambodia’s application for listing the Temple as a UN World Heritage Site was approved in July 2008. On 15 October the same year, two Cambodian soldiers were killed in clashes over the Temple. The tensions eased later the same day and both countries expressed willingness to solve the question peacefully. An agreement to start demarcating out the border and withdraw all troops from the area was reached on 13 November 2008. Despite the agreement, a few clashes with reported fatalities took place during 2009.

2011 - the most violent year since 1978

2011 proved to be the most violent year in more than three decades as the interstate conflict between Cambodia and Thailand once again became active for the first time since 1978. The conflict escalated on 4 February when Thai and Cambodian troops exchanged fire in the vicinity of the Preah Vihear temple. It was unclear who provoked the clash which ended with a truce later the same day. However, the truce proved to be fragile as the movement of Thai tanks was enough to provoke renewed clashes. For three successive days, Thai and Cambodian troops exchanged fire, despite new attempts to end the violence through a ceasefire agreement on 5 February. Both sides suffered fatalities and three civilians were reportedly killed as stray bullets and rockets hit adjacent settlements. In addition, the skirmishes left thousands of civilians displaced.

In order to settle the prolonged dispute between the two states, the UN Security Council assigned the Association of Southeast Asian Nations ( ASEAN )to resolve the conflict. A step towards an increased regional involvement was taken after the February clashes when the Security Council decided to hold a three-party talk including Indonesia (ASEAN chairmanship in 2011), Thailand and Cambodia, where both parties expressed their wish for a peaceful solution. The meeting resulted in Cambodia stressing the importance of ASEAN observers at the border while Thailand showed a resilient stance regarding such a request. However, the Thai foreign ministry later changed its mind and decided to discuss the deployment of outside observers.

Despite the ostensible step towards an observation mission, Thailand proved to be resistant during the following meeting, thus continuing to stall the talks. The negotiations regarding the mission reached an inevitable deadlock in late April as Thailand demanded Cambodia to withdraw its troop before deploying Indonesian observers. As the attempt to solve the conflict faded with the Thai demand, the Thai-Cambodian relation deteriorated and new fighting erupted on 22 April in the Thai province Surin, thus the conflict had spread beyond the Preah Vihear area. Cambodia had been occupying the Ta Krabei temple in Surin and the new clashes started when Cambodian troops deployed in the area fired at Thai troops. A ceasefire was reached the same day but was quickly broken as fighting continued until 5 May. During the skirmishes, both parties accused each other of violating international law by deliberately targeting civilians. At the ASEAN summit in Jakarta on 3 May, Thailand refused to sign an agreement regarding observers, thus hampering progression once more. During this second round of fighting, both parties suffered casualties. In addition, an estimate of 45 000 people had been displaced.

On 18 July, the International Court of Justice (ICJ) brought up the Preah Vihear case after a Cambodian request to the ICJ to interpret the 1962 judgement. The decision, ruled out by the ICJ, was to establish a demilitarized zone with the withdrawal of all military personnel. In addition, Cambodia was to gain access to the temple and observers were to be allowed. However, the fighting outside the Preah Vihear temple was beyond the jurisdiction of the ICJ, thus not encompassing the Surin province.

The Temple of Preah Vihear and the ICJ ruling in 2013

On 28 April 2011, Cambodia filed an application to the ICJ to request an interpretation of the ICJ judgement of 15 June 1962. The ICJ concluded that the judgement of 1962 decided that Cambodia has sovereignty over the whole territory of Preah Vihear and that, in consequence, it required Thailand to withdraw all its troops from theterritory.

2025 - the conflict flares up again

The border conflict between Thailand and Cambodia, which had been inactive for several years, flared up once more during 2025. The first fatality occurred in May, when a Cambodian soldier was killed after an exchange of gunfire at a part of the Cambodian-Thai border that is still undelimited. This resulted in tensions between the states, a worsening of their diplomatic relations, and an increased military presence in the border region. More extensive violence followed in late July, when small arms fire quickly escalated into use of heavier weaponry. It is unclear what caused the outbreak of the clashes, which started on the 24th and lasted until the 28th of July, as both states claim the other triggered the escalation. Aside from military fatalities, 23 civilians were also killed during the July clashes and up to 300,000 people became displaced in the border region. The fatalities were primarily localized to the border along the Thai provinces Surin, Sisaket, and Ubon Ratchathani. On the Cambodian side, this corresponds to the border along the Oddar Meanchey and Preah Vihear provinces. After four days of fighting, the countries agreed to end hostilities and implemented a ceasefire following talks in Putrajaya, Malaysia. The ceasefire took effect on the 28th of July at midnight and halted clashes.

The commitment to ending hostilities continued, and on October 26th the Cambodian and Thai governments signed the Kuala Lumpur Peace Accord. The parties reiterated their commitment to peace, refrainment from use of force, and their respect for international boundaries. They also agreed to the establishment of an observation team consisting of personnel from ASEAN (Association of Southeast Asian Nations) member states, to ensure the implementation and effectiveness of the ceasefire. The parties also agreed to partake in confidence-building measures, aiming to restore and maintain mutual trust as well as decrease negative public sentiment. Furthermore, they also reaffirmed their commitment to international law and solving the border dispute through peaceful means, and using the established border committees to address such issues. The agreement was signed by both the governments of Thailand and Cambodia, as well as Malaysia and the United States who were present as witnesses.

The agreement, however, did not hold as clashes resumed a few weeks later. On December 8th, clashes broke out and escalated quickly, with both parties once again claiming the other had launched the first attack. Attacks included use of heavy weaponry, such as fighter jets and shells. The clashes continued throughout December, causing civilian fatalities and considerable displacement of civilians along the border once more. On the 27th of December, a new ceasefire was implemented, halting the clashes and freezing the frontlines. The parties also agreed to ban further military reinforcement. Although tensions remained despite the agreement, clashes halted for the remainder of the year.

During 2025, UCPD recorded 252 fatalities in the conflict between Thailand and Cambodia, with Cambodian soldiers making up more than half. Civilians were also killed, with 51 recorded fatalities in total. The highest estimate for all the conflict’s fatalities during 2025, however, was much higher at 442 fatalities.