Both important internal and external factors and their complex interplay explain how Siam (now Thailand) avoided colonialism by Western powers. Among key internal factors was the early use of “soft power” strategies by Siam’s astute nineteenth century monarchs, King Mongkut (King Rama IV), and King Chulalongkorn (King Rama V the Great). King Chulalongkorn made two lengthy trips to Europe to cultivate key European leaders, and he invited Russia’s future czar to visit Siam where he was received lavishly. This approach was chosen rather than to try to build up a powerful Siamese army to fight colonial wars. Also wisely these two monarchs openly invited Europeans to come to Siam to help the country modernize in numerous areas and they were also open to missionary influence, which was particularly strong in education and medicine. In terms of pragmatic diplomacy, Siam was willing to cede some territory to England and France. Another key internal factor was that Siam’s rich agricultural resources were not of any real interest to Europe. In terms of external factors, a key one was England and France’s rivalry to try to control Siam. The British did not want the French to control Siam, and the French did not want the British to control Siam. So that too helped keep Siam independent. During World War II, Thailand avoided colonialization by Japan and related death and destruction by pursuing brilliant “bamboo diplomacy” by its leaders Pibul and Pridi. Based on the analysis of events that transpired in different historical epochs, the key to Thailand’s success in never having been a colony can be best explained by the term, shrewd manipulative bamboo diplomacy, and the early effective use of soft power.