A Comparative Analysis of Mental Health Outcomes in Heterosexual and Sexual Minority University Students

University students from diverse sexual orientations encounter specific mental health challenges due to academic demands, minority stress, and societal stigma; however, research focusing on these issues is still scarce in Southeast Asia. This research aimed to examine the mental health outcomes of heterosexual and sexuality-diverse students in Thailand, concentrating on both negative aspects—such as depression, anxiety, and perceived stress—and positive aspects—like resilience, inner strength, and perceived social support. A cross-sectional survey was performed with 442 university students aged between 20 and 30, employing validated self-report instruments. Statistical methods, including t-tests and multiple regression analyses, were used to evaluate differences and relationships between sexual orientation and mental health outcomes while controlling for confounding variables. The findings revealed that sexuality-diverse students showed notably higher levels of depression (B = 0.115, p < 0.05) and lower perceived social support (B = −0.10, p < 0.05) when compared to their heterosexual counterparts. Nevertheless, there were no significant differences found in anxiety, perceived stress, resilience, or inner strength. Perceived social support proved to be a crucial protective factor, with greater levels linked to reduced depression, anxiety, and perceived stress (p < 0.01). These results underscore the necessity for inclusive university policies, specific mental health interventions, and peer and family support initiatives to enhance the well-being of sexuality-diverse students in Thailand.