The large existing commercial buildings and their electricity consumptions in Thailand have been surveyed and categorized into five types: (1) Office, (2) Hotel, (3) Education, (4) Hospital, and (5) Retail store. As the results, the commercial buildings have generally behaved significant roles on the total electricity consumption in Thailand. Therefore, the five types of generic reference building (GRB) are modeled and transferred into the building simulation tool called DOE-2.1E. This paper presents the parameterization study of the impacts and sensitivity of building envelope parameters and energy conservation options for each building type on the electricity consumption in the commercial sector and whole country. The parameterization study of the building envelope parameters and energy conservation options includes shading coefficient of window (SC), overall heat transfer coefficient of fenestration (Uf), heat transfer coefficient of opaque wall (Uw), window-to-wall ratio (WWR), lighting power (LP), equipment power (EP) and coefficient of performance (COP). Finally, the recommendations of sensitive analysis of building parameters for assessing the energy conservation options (ECO) for each building type, subjected to weather data of Thailand, are proposed.