The aim of this study was to assess the prevalence of alcohol use and misuse, and to identify its associated factors among in-school adolescents in the 2015 Thailand Global School-based Student Health Survey (GSHS). The sample included 5994 school-going adolescents (mean age 14.5 years, SD = 1.7) from Thailand that responded to the 2015 GSHS. Overall, 22.2% were current alcohol users, 24.3% had ever been drunk, 12.1% had drunk two or more alcoholic drinks in a day in the past 30 days and 10.8% had gotten into trouble because of drinking alcohol. In adjusted Poisson regression analysis, older age, psychological distress, current tobacco use, the consumption of one or more soft drinks a day, school truancy, having been in a physical fight in the past 12 months, and having been seriously injured in the past 12 months were associated with current alcohol use. Older age, psychological distress, current tobacco use and injury also increased the odds for lifetime drunkenness, having two or more drinks in a day and trouble resulting from drinking. Soft drink consumption and having been in a physical fight also increased the odds for lifetime drunkenness and having two or more drinks in a day and school truancy also increased the odds for lifetime drunkenness and trouble resulting from drinking. In addition. Parental tobacco use was associated with lifetime drunkenness and trouble resulting from drinking, cannabis use with trouble resulting from drinking, and parental support was protective from trouble resulting from drinking. There were no significant sex differences regarding any of the four alcohol use indicators. More than one in five school-going adolescents in Thailand use and misuse alcohol, and strategies to prevent alcohol misuse, including a cluster of risk behaviours, are needed.