This paper explores family and non-family factors contributing to happiness among students aged 15-18 in Thailand. Data come from the Social and Cultural Situation and Mental Health Survey (n = 905). Based on regression analysis, family factors are more important than non- family factors in explaining the variations in adolescents' happiness. Regarding the family domain, those who reported sufficient time spent with family members and highest level of love and connectedness were happiest. Those living in a two-parent family were happiest, followed by those living with a married father or a married mother (in a single parent family). Those living in an unmarried mother family were unhappiest, controlling for household economic status. These findings highlight the important role of a father in a country with a matrilocal family system. Regarding non-family factors, adolescents with the highest school attendance, highest self-esteem, and highest economic status who also regularly participated in extracurricular activities were happiest. Adolescents who were older and who had to do chores regularly tended to be less happy than their peers.