BACKGROUND: As caries prevalence in Thai preschool children is very high and its consequences have scarcely been evaluated, the Scale of Oral Health Outcomes for 5-year-old children (SOHO-5) is considered as an appropriate tool to measure the children's oral health-related quality of life (OHRQoL). AIM: To translate the SOHO-5 into Thai (Th-SOHO-5) and assess its psychometric characteristics. DESIGN: The cross-cultural adaptation of the SOHO-5 into Thai comprised forward-backward translation by experts and face validation by 20 child-parent dyads. To evaluate psychometric properties of the final version, a cross-sectional study was conducted on 306 child-parent pairs using an interview mode for children and a self-administered mode for parents. A trained investigator examined children's caries status. RESULTS: The Th-SOHO-5 showed satisfactory psychometric characteristics. Cronbach's alpha values were above 0.8 for both child and proxy reports. Overall intraclass correlation coefficients were > 0.9. Factor analysis supported a single-factor structure model of the Th-SOHO-5 and showed an excellent fit. Th-SOHO-5 scores were correlated with all global rating scales of oral health and well-being. Children with higher caries experience or caries with pulpal involvement demonstrated significantly higher Th-SOHO-5 scores. CONCLUSION: The Th-SOHO-5 possessed good reliability and validity. It can be used to evaluate the OHRQoL of preschool children in Thailand.