Conservation of historic structures are important to maintain healthy conditions of the valuable structures against adverse environmental impacts. In Thailand, plenty of historic structures require appropriate plan to conserve their present conditions. The first step is to understand the past histories of the structures. The objective of this project is to review documents related to construction and restoration works of important historic structures, the stupa of Wat Arun Rajwararam in Bangkok and Wat Yai Chaimongkol in Phra Nakhon Sri Ayutthaya. Documents were collected from reports and studies available at present. The outcome of this study and future studies are necessary for documentation of the nation’s heritage.