Inner Cambodia

It covered much of north-western Cambodia, and included, most significantly, the cities of Phra Tabong, Siammarat and Si Sophon[b] (now known by the Khmer names Battambang, Siem Reap, and Serei Saophoan).

[1] When the Prince was allowed to return to Cambodia to assume the throne in 1794, Rama I had the northwestern area of the country, which constituted most of its border with Siam, placed under the control of Baen, who was instituted as governor of the region, based in Battambang (known in Thai as Phra Tabong).

Siem Reap (Siam Rap in Thai,[e] later changed to Siammarat), the site of the ancient Khmer capital of Angkor, was the other major town in the region, the most fertile in Cambodia.

While Khmer sources would later dispute the act, stating that the arrangement was originally understood to be limited to Baen's lifetime, it established the hereditary succession which placed rule over the region in the hands of the Abhayavongsa family for much of the following century, except for the period between 1834 and 1839, when the Thai court granted the role to the Cambodian prince Ang Im.

[3][4] He also founded the towns of Mongkhon Buri[f] (now Mongkol Borey) and Si Sophon (Serei Saophoan), the latter of which was mainly populated by Lao forced settlers following Siam's conquest of Vientiane in the 1826–1828 war.

[11] Despite its location in Siam, the French were able to secure permission for exploration and study of Angkor's sites, and developed Angkorian art and architecture into a symbol of Cambodian national identity.

[18][19] In the prelude to the Pacific theater of World War II, the nationalist government of Thai Prime Minister Plaek Phibunsongkhram invaded French Indochina in 1940 to pursue its irridentist pan-Thai ideology and reclaim what it regarded as Thailand's lost territories.