The purposes of this research were : 1) to study process and development of becoming male sex workers regarding background, living condition, working condition and attitude towards male sexual services and 2) to study trends in leading future life of male sex workers. The sample group, 10 male sex workers working in gay bars in Chiang Mai Province, was purposively selected. The data were collected by participant observations, informal interviews and group discussions. The data were inductively analyzed by relating data and events to draw conclusions. It was found that the process and development stages of ecoming male sex workers were as follows: 1. The stage of entering male sex worker professionFrom the study of male sex workers background, it was found that there were similarities in their age and poor education which caused them to base their decision makings mostly on their impulse. Moreover, family problems, such as parents death, their conflicts, and their separations were found to affect in adequate love and warmth for the youngsters and drive them from home to lead their own lives. This was when self-dependent, income, and jobs became their main interests.Besides their personal problems, the youngsters contact and interactions with sex workers had led them to accept the violation of social rules about sex and develop a positive outlook towards sexes as a source of income. Such a positive attitude was a crucial factor that caused youngsters to enter the sex service profession. Therefore, the starting point of entering the sex worker profession was the youngsters acceptance of the violation of social rules about sex. 2. The stage of learning and adapting to new cultureSince their sexual behaviors violated the social rules about sex of the main society, the youngsters had to learn to adapt to their new way of living. They learned to follow the rules and adapt to the culture of their "new" social group although their rules and culture were different from those of the main society. The youngsters learned to adapt themselves to the "new" culture through interactions with those with similar careers. So as not to feel guilty, they made themselves believe that they had entered the sex business because of necessities and attractive earnings. This self-justification enabled them to keep violating the social rules about sex continuously and permanently in the long run.Trends in leading future life of male sex workers After working as male sex workers for a period of time, they wished to go back and be accepted in the main society, running such business as a bar-beer, a grocery shop, or working in a company. Their deal was that they had to make enough money first before they a started new life within the norms of the main society.