The contribution of foreign historical accounts to the formation of the history of Siam has been well established in previous scholarship. Various reports are available in different languages concerning the Siamese court, people and culture, especially during the Ayutthaya period. This lecture, which is part of the researcher’s long-term project, presents new evidence in relation to Siamese earlier social and cultural contexts. Based on this discovery, we are now able to identify some of the foreign residents of Siam of the time and how they contributed to Siamese society from Tenasserim to Ayutthaya.