Men who have sex with men (MSM) remain one of the most at-risk populations for HIV infection in Thailand, and young MSM (YMSM) may be particularly at risk due to developmental factors. YMSM engage in high rates of condomless anal sex (CAS), which is a key driver of HIV infection. Substance use behaviors, such as binge drinking and stimulant use, are associated with CAS among people living with HIV in high-income countries. However, results of similar studies conducted among YMSM living with HIV in Thailand are inconclusive, limiting our ability to develop tailored prevention strategies for this group. The purpose of the current study was to evaluate the associations between substance use (binge drinking and stimulant use) and CAS among Thai YMSM living with HIV, and to assess whether these associations are moderated by age. Data for the current study were drawn from a longitudinal study of 214 MSM living with HIV in Bangkok, Thailand between the ages of 18-29 years old. Only data from the baseline survey were used for the purpose of the present analyses. Data were collected using an online survey, which collected demographic information and assessed CAS, binge drinking, and stimulant use. Bivariate and multivariable logistic regressions were used to assess the associations between substance use (e.g., stimulant use or binge drinking) and CAS, and whether age moderated these associations. Binge drinking was positively associated with CAS in the present sample; however, age and stimulant use were not associated with CAS. The findings from the current study suggest a need to address binge drinking in secondary prevention interventions among Thai YMSM living with HIV.