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 Maoist dictator Pol Pot (Saloth Sâr).

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.

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.

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.

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.

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.

Cambodia's military commander said: "A wing of our Preah Vihear temple has collapsed as a direct result of the Thai artillery bombardment".

[13] 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".

[20][21] 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.

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.