This account of Japan-Thailand economic relations traces developments from the minimal trading with Meiji Japan to the place planned - but never put into effect - for Thailand to have a major role in the New Economic Order of the Co-Prosperity Sphere. Siam-Japan trade is shown to have increased in the 1920s with Japan's supply of manufactured goods, hampered by attempted Chinese boycotts in 1928. 1931 and 1937 though Thailand increasingly supplied rubber and agricultural produce. After the Thailand-Japan political agreement of December 1941 the Thai Central Bank was established. It is shown that full integration with some independence within the Co-Prosperity Sphere was in train when Japan's plans were dashed in August 1945. With appended documents and correspondence, bibliography and index.