Territorial losses of Thailand

The territorial losses of Thailand is a concept in Thai historiography, referring to episodes of conflict in the Rattanakosin-period history of Thailand (or Siam as the country was historically known) where the country was forced to cede territory, especially to the Western colonial powers of France and Great Britain during the reign of King Chulalongkorn (Rama V, 1868–1910).

One version of the map of Thailand's territorial losses, listing eight instances of losses to France and the British Empire

The concept was first popularized in the 1930s as part of the anti-Western Thai nationalist ideology promoted by the government of Plaek Phibunsongkhram. The loss of territories was leveraged as a theme in "national humiliation discourse"—as termed by historian Shane Strate—which was employed to bolster support for the government and its irridentist ideology of Pan-Thaiism.[1][2]

The list of lost territories was publicized through a widely reproduced map, titled the Map of the History of Thailand's Boundary, which showed several areas claimed as historically part of Thailand, numbered and labelled with the dates of their loss. The map has since been reproduced in several versions, including by historians as the concept became embedded in conventional historiography; most Thais are familiar with it through its inclusion in a widely used student atlas.[3]

The concept remains a mainstay in Thai nationalist discourse, and has re-emerged especially during episodes of the Preah Vihear Temple dispute with Cambodia in 1959 and 2008. The case itself has become regarded as one of the losses in recent versions of the map and list that proliferated online in the 21st century, claiming up to fourteen losses as opposed to the original eight.[4]