In 1904, Siam and the French colonial authorities ruling Cambodia formed a joint commission to demarcate their mutual border. In the vicinity of the temple, the group was tasked by the two governments to work under the principle that the border would follow the watershed line of the Dângrêk mountain range, which places Preah Vihear on the Thailand side. In 1907, after survey work, French officers drew up a map to show the border’s precise location. The resulting map, which was sent to Siamese authorities, showed Preah Vihear as being on the Cambodian side.

In 1954, Thai forces occupied the temple following the withdrawal of French troops from Cambodia. Cambodia protested and in 1959 asked the International Court of Justice to rule that the temple lay in Cambodian territory. The case became a volatile political issue in both countries. Diplomatic relations were severed, and threats of force voiced by both governments.

The court proceedings focused not on questions of cultural heritage or on which state was the successor to the Khmer Empire but on technicalities of the border demarcation work early in the century and Thailand's subsequent treatment of the resulting map.

Arguing in the Hague for Cambodia was former U.S. secretary of state Dean Acheson, while Thailand’s legal team included a former British attorney general, Sir Frank Soskice. Cambodia contended that the map showing the temple as being on Cambodian soil was the authoritative document. Thailand argued that the map was invalid, was not an official document of the border commission, and violated the commission’s working principle that the border would follow the watershed line, which would place the temple in Thailand. If Thailand had not protested the map earlier, the Thai side said, it was because Thai authorities had practical possession of the temple, due to the great difficulty of scaling the cliff from the Cambodian side, or had not understood that the map was wrong.

On June 15, 1962, the court ruled 9 to 3 that the temple belonged to Cambodia and, by a vote of 7 to 5, that Thailand must return any antiquities such as sculptures that it had removed from the temple. In its decision, the court noted that over the five decades after the map was devised, the Siamese/Thai authorities did not object in various international forums to the map’s depiction of the temple’s location. Nor did they object when a French colonial official received the Siamese scholar and government figure Prince Damrong at the temple in 1930. Thailand had accepted and benefited from other parts of the border treaty, the court ruled. With these and other acts, it said, Thailand had accepted the map and therefore Cambodia was the owner of the temple.

Thailand reacted angrily. It announced it would boycott meetings of the Southeast Asia Treaty Organization, with Thai officials saying this step was to protest a U.S. bias toward Cambodia in the dispute. As evidence, Thai officials cited the pro-Cambodia vote of an American judge on the court and Acheson’s role as Cambodia’s advocate; the U.S. government replied that Acheson was merely acting as a private attorney, engaged by Cambodia. Mass demonstrations were staged in Thailand protesting the ruling.

Thailand eventually backed down. In January 1963, Cambodia formally took possession of the site in a colorful ceremony attended by close to 1,000 people, many of whom had made the arduous climb up the cliff from the Cambodian side. A fit Prince Sihanouk, Cambodia’s leader, bounded up the cliff in less than an hour, paused to sip lemonade, then made offerings to Buddhist monks. In the ceremony, he made a gesture of conciliation, announcing that all Thais would be able to visit the temple without visas, and that Thailand was free to keep antiquities that it had taken away from the site.^[3]

Full-scale war began again in Cambodia in December 1978 when the Vietnamese army invaded to overthrow the Khmer Rouge. Khmer Rouge troops retreated to border areas. In January, the Vietnamese reportedly attacked Khmer Rouge troops holed up in the temple, but there were no reports of damage to it. Large numbers of Cambodian refugees entered Thailand after the invasion. In June 1979, Thai security forces forcibly expelled tens of thousands of them back into Cambodia in the vicinity of Preah Vihear. Unknown numbers were killed by landmines, gunfire and exposure; the government that Vietnam installed in Phnom Penh put the number of fatalities at more than 300.

Guerilla warfare continued in Cambodia through the 1980s and well into the 1990s, hampering access to Preah Vihear. The temple opened briefly to the public in 1992, only to be re-occupied the following year by Khmer Rouge fighters. In December 1998, the temple was the scene of negotiations by which several hundred Khmer Rouge soldiers, said to be the guerrilla movement's last significant force, agreed to surrender to the Phnom Penh government.^[5]

The temple opened again to visitors from the Thai side at the end of 1998; Cambodia completed the construction of a long-awaited access road up the cliff in 2003.

As the process of Heritage-listing began, Cambodia announced its intention to apply for World Heritage inscription by UNESCO. Thailand protested that it should be a joint-effort and UNESCO deferred debate at its 2007 meeting.

Following this both Cambodia and Thailand were in full agreement that Preah Vihear Temple had "Outstanding Universal Value" and should be inscribed on the World Heritage List as soon as possible. The two nations agreed that Cambodia should propose the site for formal inscription on the World Heritage List at the 32nd session of the World Heritage Committee in 2008 with the active support of Thailand. This led to a redrawing of the map of the area for proposed inscription, removing the 4.2sq kilometres of border territory awarded to Cambodia but still occupied by Thailand and leaving only the temple and its immediate environs.

Thailand's political opposition launched an attack on this revised plan (see New dispute over ownership) , claiming the inclusion of Preah Vihear could "consume" the overlapping area of the dispute lands. In response to the political pressure at home Thailand withdrew its formal support for the listing of Preah Vihear Temple as a World Heritage site.

Cambodia continued with the application for World Heritage status and, despite official Thai protests, on July 7, 2008 (July 8th in Cambodia) , Preah Vihear Temple was inscribed on the list of World Heritage sites.

The temple can be approached from Kantharalak district, Sisaket Province of Thailand. Cambodia allows day-trip access to the temple on a visa-free basis from Thailand. Cambodia imposes an entrance fee of US$5 or 200 baht for foreigners (as of 2006, reduced to 50 baht for nationals of Thailand) , plus a fee of 5 baht for processing a copy of the passport. In addition, Thailand imposes an access fee of 400 baht for entering the National Park.

Cambodia has from time to time cut off access from Thailand during times of dispute with the Thai government.

The approach to the sanctuary is punctuated by five gopuras (these are conventionally numbered from the sanctuary outwards, so gopura five is the first to be reached by visitors). Each of the gopuras before the courtyards is reached by a set of steps, and so marks a change in height which increases their impact. The gopuras also block a visitor's view of the next part of the temple until he passes through the gateway, making it impossible to see the complex as a whole from any one point.

The fifth gopura, in the Koh Ker style, retains traces of the red paint with which it was once decorated, although the tiled roof has now disappeared. The fourth gopura is later, from the Khleang/Baphuon periods, and has on its southern outer pediment, "one of the masterpieces of Preah Vihear" (Freeman, p. 162) : a depiction of the Churning of the Sea of Milk. The third is the largest, and is also flanked by two halls. The sanctuary is reached via two successive courtyards, in the outer of which are two libraries.