Plaek Phibunsongkhram in the context of Thai cultural mandates

Before and during World War II, the Empire of Japan created a number of puppet states that played a noticeable role in the war by collaborating with Imperial Japan. With promises of "Asia for the Asiatics" cooperating in a Greater East Asia Co-Prosperity Sphere, Japan also sponsored or collaborated with parts of nationalist movements in several Asian countries colonised by European empires, the Soviet Union, and the United States. The Japanese recruited volunteers from several occupied regions and also from among Allied prisoners-of-war.

Some of the leaders in various Asian and Pacific territories cooperated with Japan as they wanted to gain independence from the European colonial overlords, as seen in Burma and Indonesia. Some other collaborators were already in power of various independent or semi-independent entities, such as Plaek Phibunsongkhram's regime in Thailand, which desired to become a major player in Asian politics but were restrained by geopolitics, and the Japanese maximised it to some extent. Others believed Japan would prevail, and either wanted to be on the winning side, or feared being on the losing one.

The Franco-Thai War (October 1940 – 28 January 1941, Thai: กรณีพิพาทอินโดจีน, romanized: Karani Phiphat Indochin; French: Guerre franco-thaïlandaise) was fought between Thailand and Vichy France over certain areas of French Indochina.

Negotiations shortly before World War II had shown that the French government was willing to alter the boundaries between Thailand and French Indochina, but only slightly. Following the Fall of France in 1940, Major-General Plaek Phibunsongkhram (popularly known as "Phibun"), the prime minister of Thailand, decided that France's defeat strengthened the Thais' negotiating position to regain the vassal state territories that were ceded to France during King Chulalongkorn's reign.

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

The concept was popularized in the 1930s as part of the Thai nationalism promoted by the government of Plaek Phibunsongkhram. The idea was propagated through sets of maps, titled the Historical Atlas of Thailand and Map of the History of Thailand's Boundary, that claimed to depict the historical extent of the boundaries of Thailand's predecessor states and the territories it subsequently lost. The maps have been widely disseminated, especially through their inclusion in Thongbai Taengnoi's student atlas, a standard textbook used in Thai schools since 1963.