Cambodia–Thailand border
The Cambodia–Thailand border is the international border between Cambodia and Thailand. The border is 817 km in length and runs from the tripoint with Laos in the north-east to the Gulf of Thailand in the south.
Description
The border starts in the north-east at the tripoint with Laos at Preah Chambot peak in the Dângrêk Mountains and follows the crest of the mountains westwards. Upon leaving the mountains the border turns south-westwards in a broad arc, occasionally utilizing rivers such as the Svay Chek, the Sisophon, the Phrom Hot and Mongkol Borei. It then proceeds south, partly along the Cardamom Mountains, terminating at the Gulf of Thailand coast. This latter section runs very close to the Gulf, producing a long, thin strip of Thai territory.History
Colonial period
The boundary area has historically switched back and forth between various Khmer and Thai empires. From the 1860s France began establishing a presence in the region, initially in modern Cambodia and Vietnam, and later Laos, with the colony of French Indochina being created in 1887. In 1867 a Franco-Thai treaty confirmed Thai ownership of the Battambang and Angkor regions. In 1896, Britain and France agreed to leave Siam as a buffer state between their respective colonies. However France continued to expand at the expense of Siam, annexing northern Cambodia in 1904 and then Battambang, Sisophon and Siem Reap in 1907, whilst ceding Trat to Siam. The modern Cambodian-Thai border was as such delimited through several treaties between France and Siam between 1867 and 1907. Following the Japanese invasion of French Indochina in 1940 areas ceded to France in 1904 and 1907 were returned to Thailand, however this was reversed following Japan's defeat and the pre-war border restored in 1946.Since Cambodian independence
Cambodia gained independence in 1953, and since then the two states have had a fractious relationship. A Cambodian–Thai border dispute arose in the late 1950s over the ownership of Preah Vihear, a temple in the Dângrêk Mountains, adjacent to the border. In 1962 the case was referred to the International Court of Justice, which ruled in favour of Cambodia, however Thailand expressed reservations as to the outcome. The mid-1960s also saw a dispute over ownership of Ko Kut island. These disputes faded as Cambodia became engulfed in a series of conflicts in the following decades and the disastrous rule of the Khmer Rouge, with thousands of refugees crossing the border. By 1981, over 250,000 Cambodian and Vietnamese refugees lived in twenty camps along the border, supported by international aid agencies and the United Nations Border Relief Operation.Sporadic fighting broke out along the border following Vietnam's invasion of Cambodia in 1979 which forced the Khmer Rouge to flee to camps on the border with Thailand, using them as a base throughout the 1980s until Vietnam withdrew from the country in 1989. On 18 February 1994, the Khmer Rouge led by Pol Pot rebuilt their headquarters at Dângrêk Mountains located in Anlong Veng near the Thai border. In an effort to stop Khmer Rouge infiltration from Thailand, Cambodia built a large fortified fence along the border in the second half of the 1980s.
Since the advent of peace in Cambodia in the early 1990s relations with Thailand have once again soured over the Preah Vihear issue, as well as, to a lesser extent, Ko Kut island. A border commission was set up in 1995 in an attempt to settle the issues peacefully, however by 2013 it had made little progress and a full border demarcation satisfactory to both sides remained outstanding.
Armed fighting broke out at various times from 2008 to 2011. As of September 2022, government officials said border demarcation had been completed in 13 areas, and that the remaining 11 were under negotiation.
On 28 May 2025, one Royal Cambodian Army soldier was killed after a Thai patrol encountered Cambodian soldiers digging trenches. Both Cambodia and Thailand accused the other of trespassing on their respective territories and firing first. Phumtham Wechayachai, Thailand's Defense Minister, claimed that opening fire was not intended on both sides. Cambodia stated that it will litigate the dispute with the International Court of Justice.
In July 2025, the conflict was reignited with both sides' military attacking each other. Thailand also sealed all land border crossings with Cambodia. Multiple civilians were reported to be killed. On 24 July 2025, Cambodian Prime Minister Hun Manet submitted a request to the United Nations Security Council to call for an urgent meeting to stop Thai aggression. The UNSC held the meeting on 25 July 2025. With mediation effort from 2025 ASEAN Chair country Malaysia, as well as call for a ceasefire from U.S. President Donald Trump to both countries, Hun Manet and Thailand Acting Prime Minister Phumtham Wechayachai met in Kuala Lumpur for peace talks on 28 July 2025. Both countries agreed on an immediate and unconditional ceasefire taking effect on on 29 July 2025. On 8 December 2025, after both countries reported violations of the ceasefire, fighting across the border resumed until another ceasefire agreement was signed on 27 December.