In Thailand physical violence among male adolescents is considered a significant public health issue, although there has been little published research into the aetiology and functions of violence in Thai youth. Research in this area has been hampered by a lack of psychometrically sound tools that have been validated to assess problem behaviours in Asian youth. The purpose of this paper is to provide validity and reliability data on an instrument to measure violence in Thai youth. In this study, reliability and validity data for a sample of adolescent Thai youth are reported for the Communities That Care Youth Survey (CTC-YS), a measure of risk and protective factors for violent behaviour, and the STAXI-II, a measure of angry experience and expression. The findings showed overall high internal consistency for both questionnaires, and there was evidence of construct validity. It is concluded that these measures are appropriate for use in research that seeks to investigate youth violence among adolescents in Thailand.