BackgroundAssessment of health disparities between population groups is essential to provide basic information for resource prioritization in public health. The objective of this study is to assess the extent that behavioral health outcomes and experience of violence varied between cisgender heterosexual adolescents and those who identified as lesbian, gay, bisexual, transgender, queer and questioning, and asexual (LGBTQA+) in the 5th National School Survey on Alcohol Consumption, Substance Use and Other Health-Risk Behaviors.MethodsWe surveyed secondary school students in years 7, 9 and 11 in 113 schools in Thailand. We used self-administered questionnaires to ask participants about their gender identity and sexual orientation and classified participants as cisgender heterosexual, lesbian, gay, bisexual, transgender, queer and questioning, or asexual, stratified by sex assigned at birth. We also measured depressive symptoms, suicidality, sexual behaviors, alcohol and tobacco use, drug use, and past-year experience of violence. We analyzed the survey data using descriptive statistics with adjustment for sampling weights.ResultsOur analyses included data from 23,659 participants who returned adequately-completed questionnaires. Among participants included in our analyses, 23 percent identified as LGBTQA+ with the most common identity being bisexual/polysexual girls. Participants who identified as LGBTQA+ were more likely to be in older year levels and attending general education schools rather than vocational schools. LGBTQA+ participants generally had higher prevalence of depressive symptoms, suicidality, and alcohol use than cisgender heterosexual participants, whereas the prevalence of sexual behaviors, lifetime history of illicit drug use, and past-year history of violence varied widely between groups.ConclusionWe found disparities in behavioral health between cisgender heterosexual participants and LGBTQA+ participants. However, issues regarding potential misclassification of participants, limitation of past-year history of behaviors to the context of the COVID-19 pandemic, and the lack of data from youths outside the formal education system should be considered as caveats in the interpretation of the study findings.