From 1938 to 1947, Direk served in many important posts in the Thai government during the early years of constitutional rule. During World War II, he held the post of Foreign Minister to become the Ambassador to Japan. He also held the posts of Deputy Prime Minister, Foreign Minister (multiple times), Justice Minister, and Finance Minister. He also served as the
Thai ambassador to the
Court of St. James's (
England),
Germany and
Finland. In 1947, he was appointed ambassador in London, but resigned a few months later as a result of the
Phibunite coup. Direk's memoir
Thailand and World War II was first published in 1966. Direk's account is "especially good on the
Franco-Thai conflict of 1940, the
invasion by Japan in 1941, the delicate relationship with Japan over 1942–1943, financial affairs in the immediate postwar period, and the negotiations to rehabilitate Thailand with the
Allied Powers, including becoming a member of the
United Nations". ==Thammasat University==