Japanese Invasion of Thailand - Aftermath

Aftermath

Plaek Pibulsonggram's decision to sign an armistice with Japan effectively ended Churchill's hopes of forging an alliance with Thailand. He also granted Japan permission to use Thailand as a base of operations to invade Malaya. Within hours after the armistice came into effect, squadrons of Japanese aircraft had flown into Songkla airfield from Indochina, allowing them to carry out air raids on strategic bases in Malaya and Singapore from a short distance. At the time of the ceasefire, Great Britain and the United States regarded Thailand as Japanese-occupied territory.

On 14 December, Pibulsonggram signed a secret agreement with the Japanese committing Thai troops in the Burma Campaign. An alliance between Thailand and Japan was formally signed on December 21, 1941. On January 25, 1942, the Thai government declared war on the United States and the United Kingdom. In response, all Thai assets in the United States were frozen by the federal government. While the Thai ambassador in London delivered the declaration of war to the British administration, Seni Pramoj, Thai ambassador to Washington D.C., refused to do so, instead organising a Free Thai movement.