In concert with their bombing of Pearl Harbor on December 7, 1941, Tokyo launched military forces into southern Thailand. These deployments were critical to securing Japanese bases for planned invasions of British Malaya and Burma. In a secret agreement, Thailand’s ambitious leader, Field Marshal Phibun Songkhram, agreed to allow the Japanese free passage.

But the Japanese were soon pressing for a greater presence and access to Thai facilities. Soon, Phibun joined in a formal alliance with Tokyo. He was convinced he could benefit from Japan’s expansion while maintaining Thailand’s independence. On January 25, 1942, Bangkok declared war on Britain and the United States. Japanese imperial forces were quickly deployed throughout the kingdom.

But Thailand’s senior diplomat in the United States, M.R. Seni Pramoj, opposed the alliance with Japan. He refused to endorse his government’s position. In fact, Seni began to actively build a network of overseas Thais who would work to support the Allies.

Under Seni’s guiding hand, and the leadership of Gen. William Donovan’s Office of Strategic Services (OSS), the “Free Thai” movement was born. Seni brought young Thai student volunteers from universities across the United States together into a Free Thai command, which was to serve under Donovan’s OSS.

The Free Thai agents were among Thailand’s best and brightest. They set aside promising academic programs at Harvard, Cornell, the Massachusetts Institute of Technology, and elsewhere in favor of difficult military training and uncertain futures.   

Following training by the OSS, many volunteers undertook lengthy and dangerous treks from China and Indochina to make contact with supporters opposed to the Japanese presence. For months, the Free Thai forces worked to infiltrate their homeland. Many were captured, killed, or simply went missing.

Finally, on October 5, 1944, the OSS Detachment in Szemao, China, received a radio message from Free Thai agents in a Bangkok safehouse. Thereafter, other agents were dispatched into Thailand by submarine, seaplane, and airdrop.

The heroism and ingenuity of the Free Thai forces, working hand-in-hand with the OSS, set the stage for important intelligence collection. The agents provided critical support to Allied military operations in Southeast Asia and ensured Thailand’s post-war independence.