Results of an exploratory research project elaborating the contexts, patterns and specific scenarios of the commercial sexual activity of northeastern Thai men are reported. Data were collected using face-to-face surveys, focus groups, key informant interviews and observations in 32 northeastern villages (n = 744 men), 18 migrant labour camps housing sugarcane workers (n = 219 men), and five cattlemarkets in northeast Thailand. Fifty percent of married men and 43% of single men had visited female sex workers (FSW). Female sex worker visits occurred primarily prior to marriage, though 13% of married men had purchased sexual services within the past year. Nonmarital sexual activity was set within the socio-cultural frameworks of poverty, circular migration, a large commercial sex sector, and a belief system about men's sexuality and men's and women's gender roles. Sexual services were typically purchased as part of friendship group partying (paiy tiaow) and generally included heavy alcohol consumption. The most common scenario for visiting FSWs involved brothels, though cattlemarkets, festivals, and migrant labour situations were also scenarios for FSW contact. These each had unique characteristics that affected the likelihood that condoms would be used. The further the specifics of a scenario (as evaluated by men) diverged from those of brothel contact with an FSW, the less likely men were to identify this as having the potential for HIV transmission and the less likely they were to use a condom. AIDS prevention campaigns must be developed that are sensitive to the socio-cultural framework, contexts and specific scenarios within which nonmarital sexual contacts occur.