Thailand's booming tourism sector significantly contributes to the country's economy. Sex tourism is also popular in Thailand, where male sex workers are more at risk to HIV threats than their female counterparts. Social marketing campaigns have been useful in addressing several problematic behaviours, such as smoking, binge drinking, unprotected sex and unhealthy dietary practices. Hence, the main purpose of this research study is to propose a conceptual framework for promoting safe sex practices to male sex workers in Thailand. The Theory of Planned Behaviour (TPB) has been generally applied to help understand and examine behavioural change intentions, and develop behavioural change initiatives. TPB attempts to identify the psychological determinants of behavioural change intention in a single point of time. However, it does not show how behavioural change occurs as a process, or at various stages. As this theory is not adequate for understanding the entire process of behavioural change, a more comprehensive theoretical framework is required. Combining the Theory of Planned Behaviour with the Stages of Change Theory (SCT) provides a highly comprehensive theoretical framework. The Stages of Change Theory is used in the social marketing field to facilitate behavioural change. SCT shows the behaviour change as a process. The implications of this new framework for both theory and practice are discussed, as well as the directions for future research, which would be of use to researchers and practitioners in the social marketing field.