The Treaty between Thailand and Japan Concerning the Continuance of Friendly Relations and the Mutual Respect of Each Other's Territorial Integrity was concluded in Tokyo on June 12, 1940 between the Thai and the Japanese governments.
The treaty was a step in co-operation between the Thai and the Japanese governments, which eventually became allies in the Second World War.
The Japanese government was keen to exploit the situation to gain control over French Indochina.
The Kingdom of Thailand had a common border with Indochina and so was viewed by Tokyo as a possible ally against the French control of that area.
The growing co-operation between the Thai and the Japanese governments in the wake of the treaty led the Thais to wage a brief and successful war against French Indochina in 1940-1941, which resulted in some territorial conquests for Thailand with Japanese assistance.