The article focuses on the relationship between the United States of America and the Kingdom of Thailand before and after World War II. The author first seeks to show how this relationship developed in the 19th and early 20th centuries and what the salient characteristics of it were. The second part of the article describes the American attitude toward Thailand during the war and the importance of wartime events for the future of the Thai-American relationship. Finally, the closing section deals mainly with the postwar developments and the reasons for the emergence of the strategic partnership between Bangkok and Washington. Attention is paid to the motivations and expectations of both sides, as it relates to their cooperation. The aim of the article is mainly to show the changed nature of this bilateral relationship, resulting from World War II and events that followed closely in its wake. It also seeks to point out that the common struggle against communism, although important in later years, was neither the sole nor the prevalent reason for the newly emerging American interest in Thailand in the immediate postwar period.