The Annex I map at 1:200,000 scale was prepared in Paris by French officers acting under the 1904 Franco-Siamese Boundary Convention. A Mixed Commission with Siamese members worked the demarcation between 1904 and 1907. In 1908, French authorities completed a full original distribution of approximately one hundred and sixty sets of eleven maps each, of which fifty sets were allocated to the Siamese Government. The map entered Siamese ministerial files that year.
In its 1962 judgment in the Temple of Preah Vihear case, the International Court of Justice found that Siamese receipt and decades of use without objection constituted acceptance. The Court held that the acceptance of the Annex I map by the Parties caused the map “to enter the treaty settlement and to become an integral part of it.” Thailand was bound. The Court’s 2013 interpretation judgment reaffirmed the Annex I line as central to the 1962 reasoning, and fixed Cambodian territory in the north as extending to that line but no farther. What Thailand was bound to in 1962 cannot be unbound by declaration in 2026.
On 27 May 2026, Thai Prime Minister Anutin Charnvirakul told reporters at the Thaifex Anuga Asia 2026 exhibition in Bangkok that the 1:200,000 scale “no longer exists” for Thailand’s administration. He said Thailand uses 1:50,000 maps in specified sectors and asked UNESCO to hear Thailand before publishing any heritage assessment. The Thai-language Naewna report carried an additional clause, here rendered into English from the Thai: if Cambodia still uses the 1:200,000 scale, they “do not need to come and talk to Thailand.”
On 26 October 2025, Anutin had already told Nation Thailand that Thailand had never accepted the 1:200,000 map, and that future boundary negotiations would use LiDAR survey to render the older instrument obsolete. Seven months later, the prime minister returned from a 25 May dinner at the Élysée Palace with President Emmanuel Macron, where both sides announced they would advance the France-Thailand 2026-2028 Joint Action Plan toward strategic partnership. The position held. The verbal claim does not reach the document.
On 15 June 2025, at the sixth Cambodia-Thailand Joint Boundary Commission session in Phnom Penh, the Cambodian Minister in charge of Border Affairs, Lam Chea, recorded Cambodia’s position: only the 1:200,000 map is recognised, on the basis of the 1904 and 1907 Franco-Siamese instruments. The same day, Cambodia submitted to the ICJ Registrar a formal request concerning four contested zones along the Cambodia-Thailand border: Prasat Ta Moan Thom, Prasat Ta Moan Toch, Prasat Ta Krabei, and the Mom Bei area. The submission was delivered at The Hague at 11:30 on 16 June.
On 23 October 2025, Cambodian Prime Minister Hun Manet posted that both sides had agreed at the 21-22 October Special JBC in Chanthaburi to continue joint measurement using 1:200,000 scale maps in line with the 1907 Treaty. The Thai Prime Minister’s Office and the Foreign Ministry spokesperson denied the formulation within twenty-four hours, stating that no such agreement on map scale was reached. By 4 February 2026, Hun Manet had written formally to President Macron requesting French archival access to the Franco-Siamese Border Commission records held at the Archives Nationales d’Outre-Mer. France replied through institutional channels. On 25 February 2026, French Foreign Minister Jean-Noël Barrot met Cambodian Deputy Prime Minister and Minister of Foreign Affairs and International Cooperation Prak Sokhonn. The French foreign ministry readout stated France was ready to facilitate the two parties’ access to the archives in its possession linked to the demarcation of the border, and described its engagement as completely impartial. The 117-year archive chain is open.
The 1:50,000 series Anutin cited as Thailand’s working instrument is described in regional reporting as a unilateral Thai map drawn under United States technical assistance in the postwar era. The series carries finer cartographic resolution. It does not carry treaty title. The 1962 Court did not adjudicate a 1:50,000 map. It adjudicated the Annex I map at 1:200,000 scale.
On 10 December 2025, the UNESCO World Heritage Centre issued a public statement on the border situation, citing obligations under the 1954 Hague Convention for the Protection of Cultural Property in the Event of Armed Conflict and the 1972 World Heritage Convention. The Centre recorded that it had communicated to all parties concerned the geographic coordinates of inscribed sites and sites of national significance. Anutin’s request that UNESCO hear Thailand first arrived five months after the Centre had already engaged both parties on the protection of those sites.
Article I of the MoU 2000 on the Survey and Demarcation of the Land Boundary binds the work to the 1904 Boundary Convention, the 1907 Treaty, and the maps produced by the Commissions of Delimitation. The instrument was registered at the United Nations Treaty Series as No. 48557. France holds the archives those Commissions produced. The same prime minister who met President Macron at the Élysée on 25 May, where both sides announced they would advance the France-Thailand 2026-2028 Joint Action Plan, reached Bangkok forty-eight hours later to declare the 1:200,000 instrument extinct.
The archive request is on file with France. The ICJ filing is on the docket. The Annex I map was bilaterally produced, received by Siam in 1908, and bound on Thailand by the 1962 judgment.