Prime Minister Phibunsonggram of Thailand

Phibunsonggram assumed office as Prime Minister of Thailand 

in succession to Phra Phahol in December 1938.

Besides the Premiership, Phibunsonggram also held the portfolios of Defense and Interior. These two posts as well as that of Army Commander-in-Chief assured him of close control over the armed forces and all provincial governors and national police.
Subsequently in June 1939 he took over the office of Minister of Foreign Affairs from Sri Dharmadhibes.
He changed the name of the country from Siam to Thailand and of the people from Siamese to Thai.

In the early days of December 1941, Great Britain was engaged in consultations with the United States as to the possibility of a joint public warning by both governments that if Japan went to war with Thailand it would find itself at war with both the United States and Great Britain as well. On December 6 and December 7 respectively personal message to this general effect were sent by President Roosevelt and Prime Minister Churchill to the Thai Premier. These message did not arrive in time.

The Thai Premier had no way of knowing in advance of these message which would have constituted what he might have deemed appropriate support for the successful continuation of a policy of neutrality. He thought that Thailand had been isolated by the two great Powers. He also realized that in the absence of any real prospect  of adequate military assistance, Thai resistance could not be counted upon.

He was therefore disposed to give up his determination to defend Thailand’s neutral position and reverted to being dependent upon a single dominant Power—Japan