Answer: China
Explanation: During the Second World War on one side were the Axis Powers that made up Germany, Italy and Japan. On the other hand, they were Allied Powers, the United Kingdom, the United States, the Soviet Union, France, Belgium etc. There were many other countries on the Alliance side.
China had great influence on the side of the Allies, fighting against Japan, with the help of the Soviet Union and the US. This immeasurable influence is also reflected in the Pacific battles.
Thailand was neutral at the beginning of the war, so that after the Japanese attack on Thailand and the armistice, Thailand was in some way forced to enter into an alliance with Japan.
Switzerland, like the First World War, was neutral in WWII.