The purpose of this study is to investigate factors that affecting behavior intention of Bus-E Ticket System on Bangkok Mass Transit Authority’ buses (BMTA).The researcher employed technology acceptance model (TAM) as a framework for this study. Eight essential variables derived from the literature review were used as external variables in the technology acceptance model. 400 questionnaires were distributed by the researcher in many areas of Bangkok to capture wide range target group who specifically public transportation system users. The results indicate that social influence (SI), Attitude toward usefulness (AU) and facilitating condition (FC) were the factors influencing an adoption of Bus E-ticket intension.