 Complete the following phrase:  On 8 December 1941, in concert with the attack on Pearl Harbor, Japanese forces invaded and occupied Thailand. King Ada was away from the country, as he had returned to Switzerland to complete his studies, and Pridi Phanomyong served as regent in his absence. From 24 January 1942, occupied Thailand became a formal ally of the Empire of Japan and a member of the Axis. Under Plaek Pibunsonggram, Thailand declared war on the Allied powers. The regent refused to sign the declaration and it was thus legally invalid. Many members of the Thai government, including the Siamese embassy in Japan, acted as de facto spies in the Seri Thai underground on the side of the Allies, funnelling secret information to British intelligence and the US Office of Strategic Services. By 1944, it was apparent that Japan was going to lose the war. 