The thai government was composed of collaborators but many anti japanese Thai officials were still in leading positions during the war and a FREE THAI resistance was active supplyed by the British, Australia and Americans .
After the war in 1945 the collaborators were arrested by the allies and a FREE THAI government was formed but in 1946 after the death of the king in mysterious circumstances , the Americans against the advice of UK and Australia let the Japanese collaborators out of jail and got them to form a pro USA anti communist government ,,, then many of the FREE THAI politicians were forced to leave thailand or were killed ,, a very murky period of thai history , make your own conclusions .....
Thailand was a very good ally of the USA during the cold war and vietnam period ,but the passing of the politicians from the 1946 era has lessened USA influence in Thailand .