Bilateral relations between Cambodia and Thailand date to the 13th century during the Angkor Era. The Thai Ayutthaya Kingdom gradually displaced the declining Khmer Empire from the 14th century, French protectorateship separated Cambodia from modern Thailand at the turn of the 19thâÂÂ20th centuries, and diplomatic relations between the modern states were established on 19 December 1950.
Relations between the two countries remain complicated. Incomplete demarcation of their boundaries has led to a protracted border conflict, most notably over the temple of Preah Vihear, which was brought to the International Court of Justice in 1962 but still saw military clashes emerge in 2008 and 2011. Cambodia's internal conflicts throughout the 1970s to 1980s often spilled over into Thailand, which received refugees but also gave indirect support to the Khmer Rouge led by the dictator Pol Pot (Saloth Sâr). Thailand now dominates over its poorer neighbour economically, and is the sixth largest investor in Cambodia.
Though relations are largely peaceful, the countries' peoples still bear a degree of enmity, and the two countries' shared cultural heritage has given rise to a fierce nationalist rivalry, often expressed through online flame wars over claims of ownership and origination of such heritage. These tensions have also erupted into violence when stoked by nationalist sentiments. Such episodes include a mob attack on the Thai Embassy in Phnom Penh in 2003, which prompted a downgrading of relations by Thailand. Thailand also downgraded relations in 2009 in response to the Cambodian government's support of former Thai Prime Minister Thaksin Shinawatra, while Cambodia terminated relations (represented by its embassy in Bangkok) twice in 1958 and 1961, during the Preah Vihear conflict.
In July 2025, violent clashes broke out between Thailand and Cambodia along their disputed border, resulting in over 30 deaths and the displacement of more than 270,000 people. 27 December 2025, both countries mutually agreed for ceasefire after long border disputes.
Following Jayavarman VII's death, the Khmer Empire experienced a gradual decline. Important factors were the neighboring peoples (Thai and Cham), chronic interdynastic strife, and the gradual deterioration of the complex irrigation system that had ensured rice surpluses. In the mid-13th century, the kingdom of Sukhothai was founded when a local Tai ruler declared independence from Khmer rule. It was a small local power until Ramkhamhaeng inherited control of the kingdom in 1279. During the 13th century, Thai people began to rise up, Jayavarman VIII suffered a devastating war against the Sukhothai Kingdom led by Si Inthrathit. The Angkorian era existed until 1431, when the Thai under Borommarachathirat II, captured Angkor Thom and the Cambodian king fled to the southern part of the country.
In 1594, Thailand captured the new capital at Longvek. The Thai military dismantled the Khmer administrative elite and took thousands of prisoners back to Thailand. Cambodia was reduced to a tributary state of Thailand, and for the next several centuries, its kings were often appointed or vetted by the Thai court.
Thailand annexed western Cambodia from 1795 until 1907, when Thailand had to cede these territories to France.
After Cambodia became a point of power struggle between Thailand and Vietnam, Thailand seized all power from Cambodia. Cambodia became a vassal state of Siam, but to prevent the two neighbors, Siam and Vietnam, from taking over Cambodia, King Norodom invited France to make Cambodia its protectorate, on 11 August 1863. Cambodia remained under France's rule until 9 November 1953.
In 1941, Thailand invaded French Indochina. After a brief conflict, a treaty was signed that forced France to give the western parts of Cambodia to Thailand. In 1946, following Allied victory in WWII, Thailand was forced to return these territories to France.
In 1954, after French withdrawal, Thai military forces occupied the specific grounds of the Preah Vihear Temple in Cambodia and the surrounding "gray zones." They remained until a 1962 International Court of Justice (ICJ) ruling gave the temple to Cambodia.
During the 1970s, Khmer Rouge ruled Cambodia as Democratic Kampuchea carrying out the Cambodian genocide. This caused many Cambodian refugees fleeing to the Thai border to escape Pol Pot's regime.
On 1 January 1979, Vietnam invaded Kampuchea and removed Khmer Rouge from power replacing it with the Soviet-backed People's Republic of Kampuchea escalating into an eleven year war. Thailand refused to recognize the PRK and continued to support the deposed Democratic Kampuchea though Khmer Rouge and the two non-communist factions assembled the Kampuchean government-in-exile backed by the People's Republic of China, North Korea, ASEAN and the other Western powers. During that period, the Vietnamese soldiers attacked refugee camps near the Thai-Cambodian border over the course of its annual dry seasons.
By the time Communist regimes in Eastern Europe collapsed, Vietnam withdrew its troops from Cambodia in late 1989 leading up to the 1991 Paris Peace Accords which paved way for the restoration of monarchy in 1993. On 18 February 1994, Pol Pot and the Khmer Rouge had rebuilt their former jungle bases at the Dângrêk Range of Anlong Veng near the border with Thailand.
In February 2025, Thai & Cambodian police raided a Poipet building, freeing 215 foreigners from multiple countries. Their various nationalities included 109 Thais, 50 Pakistanis, 48 Indians, 5 Taiwanese, and 3 Indonesians. This was the largest number of Thais ever freed from a suspected scam centre. South-East Asian scam centres have been operating for years, but faced increased scrutiny after a Chinese actor Wang Xing was lured to Thailand with a fake job offer, abducted, and then taken to a Myanmar scam center.
In January 2003, riots broke out in Phnom Penh after a Cambodian newspaper incorrectly reported that Thai actress Suvanant Kongying had stated Angkor Wat properly belonged to Thailand. On 29 January, the Thai embassy was burned, and hundreds of Thai immigrants fled the country to avoid the violence. Cambodians in Phnom Penh burned photos of King Bhumibol Adulyadej and Thais in Bangkok protested in front of the Cambodian embassy, burning Cambodian flags. This eventually led to the Thai government to sever diplomatic ties with Cambodia. Prime Minister Hun Sen banned Thai shows and films on TV stations.
The conflict between Cambodia and Thailand over land adjoining the site has led to periodic outbreaks of violence.
A military clash occurred in October 2008. In April 2009, 66 stones at the temple allegedly were damaged by Thai soldiers firing across the border. In February 2010, the Cambodian government filed a formal letter of complaint with Google Maps for depicting the natural watershed as the international border instead of the line shown on the 1907 French map used by the International Court of Justice in 1962.
In February 2011, when Thai officials were in Cambodia negotiating the dispute, Thai and Cambodian troops clashed, resulting in injuries and deaths on both sides. Artillery bombardment in the area occurred during the conflict. The Cambodian government has claimed that damage occurred to the temple. However, a UNESCO mission to the site to determine the extent of the damage indicates that the destruction is a result of both Cambodian and Thai gunfire.
Both sides shelled the other, and both blame the other for starting the violence. On 5 February 2011, Cambodia formally complained in a letter to the UN "The recent Thai military actions violate the 1991 Paris Peace Accord, U.N. Charter and a 1962 judgment from the International Court of Justice", the letter claims. On 6 February, the Cambodian government claimed that the temple had been damaged. Cambodia's military commander said: "A wing of our Preah Vihear temple has collapsed as a direct result of the Thai artillery bombardment". However, Thai sources spoke only of minor damage, claiming that Cambodian soldiers had fired from within the temple.
ASEAN, to which both states belong, offered to mediate the issue. However, Thailand has insisted that bilateral discussions could better solve the issue. On 5 February, the right-wing People's Alliance for Democracy called for the resignation of Prime Minister Abhisit Vejjajiva for "failing to defend the nation's sovereignty".
A UNESCO World Heritage convention held in Paris in June 2011 determined to accept Cambodia's management proposal for the temple. As a consequence, Thailand withdrew from the event, with the Thai representative explaining, "We withdraw to say we do not accept any decision from this meeting."
Following a February 2011 request from Cambodia for Thai military forces to be ordered out of the area, judges of the International Court of Justice (ICJ) by a vote of 11–5 ordered that both countries immediately withdraw their military forces, and further imposed restrictions on their police forces. The court said this order would not prejudice any final ruling on where the border in the area between Thailand and Cambodia should fall. Abhisit Vejjajiva said that Thai soldiers would not pull out from the disputed area until the military of both countries agreed on the mutual withdrawal. "[I]t depends on the two sides to come together and talk," he said, suggesting that an existing joint border committee would be the appropriate place to plan a coordinated pullback. The ICJ ruled on 11 November 2013 that the area around and below the temple belongs to Cambodia and that any Thai security forces still in that area must leave.
As in the dispute over Preah Vihear, nationalist sentiments in both countries have also repeatedly contested other elements of Cambodia and Thailand's shared cultural heritage. From the 2010s, this has emerged as an online rivalry between their netizens over claims of ownership and origination of shared heritage, occasionally erupting as episodes of online outrage and flame wars when such heritage comes into the news spotlight. Major past incidents include arguments over the Lakhon Khol / khon traditional masked dance when they were being considered for inclusion on the UNESCO Intangible Cultural Heritage Lists in 2016, and the kun Khmer / muay Thai martial arts during the 2023 SEA Games.
On 28 May 2025, Cambodian and Thai soldiers exchanged fire between each near the Emerald Triangle, resulting in the death of one Cambodian soldier. Both nations accused each other of instigating the skirmish. On 19 June 2025, the Thai Ministry of Foreign Affairs summoned the Cambodian ambassador to Thailand and submitted a formal protest regarding the leaked recording, calling Cambodia's actions "a breach of diplomatic etiquette, a serious violation of trust, and undermines conduct between two neighboring countries." Thailand imposed border restrictions with Cambodia and Cambodia has banned Thai-produced films from TV.
As of 25 July 2025, the clashes between Thailand and Cambodia, which have killed at least 16 people and displaced tens of thousands of people in both countries, could âÂÂmove towards war.âÂÂ
Over 130,000 civilians in Thailand and around 38,000 in Cambodia have been reported displaced.
U.S. President Donald Trump brokered calls with both countriesâ leaders between 26 and 27 July, demanding an immediate ceasefire and conditioning U.S. trade negotiations on halting hostilities. Cambodia agreed to "immediate and unconditional" ceaseâÂÂfire talks; Thailand responded with cautious openness, urging Cambodia to show genuine commitment.
The Thai army has accused Cambodia of violating a newly agreed midnight ceasefire by launching armed attacks at several locations along their shared border, prompting Thai retaliatory responses and ongoing military negotiations, while Cambodia denies any breach of the truce. On 29 December 2025, Cambodia allegedly flew more than 250 drones into Thai territory; Thailand said the incursion violated the ceasefire agreement, just a day after both sides vowed to stop hostilities.