Clarifying the process of urban formation and characteristics of living environment in old town of Ayutthaya, this paper discusses the form of townhouses in Thailand. The research this paper is based on tries to compare forms of shophouses in Thailand with those in other regions of Southeast Asia and southern China. The previous paper clarified the typology and its transformation of shophouse in Ratanakosin area in Bangkok. In this paper, authors selected Ayutthaya to consider the formation of urban tissues and its transformation. Ayutthaya is well known as a World Heritage Historic City with many ancient monuments. One of major focuses of this paper is what and how the townhouse was introduced in Thailand. The paper is composed by historical analysis of the process of establishment and development of Ayutthaya and considerations on block formation and typology of shophouse. Analyzing the characteristics of housing conditions and form of house plan, the paper suggests that shophouse in Ayutthaya is gradually changing to modern form.