The story of spread and dissemination of Buddhism and Hinduism in South East Asia and Far East is reallya a thrilling story of Indian missionaries whose brilliant efforts in those far off lands constitute a fascinating chapter in the cultural history of the world. Unfortunately, the early Indian records have nothing to say about the activities of these noble sons on India. It is from the literatures and epigraphic records of those countries that we know their selfless work had built up a common civilization for nearly three quarters of the Asiatic continent. The Present work has thrown light on the glorious cultural bonds that existed between these countries in those days. The work presents a comparative study of the various aspects of Hinduism and Buddhism in Siam (Thailand) in early days. Based mainly on the Thai literature, it analytically discusses the different facts of Hindu-Buddhist thought, festivals and ceremonies, languagess and literatures and art and architecture as well as the important role played by both Buddhism and Brahmanism in the spread of Indian Culture in Thailand in Particular and South East Asia and Far East in general. <br /><br />