Out-of-school youth in Thailand engage in risky sexual behavior that puts them at risk for contracting HIV infection and can have other negative sexual reproductive health outcomes. No study has examined risky sexual behaviors and compared them between Thai and non-Thai out-of-school youth. The current study compares sexual risk behavior and HIV testing behavior between out-of-school Thai and non-Thai youth. We conducted face-to-face interviews in this study population in urban Chiang Mai during 2014. Participants were recruited through convenience sampling from two main sources: non-formal education centers (NFECs) and social meeting places. We recruited 924 youth, aged 15-24 years, of whom 424 (45.9%) were Thai and 500 (54.1%) were non-Thai. The majority were attending NFECs (82.3%). Of the sexually experienced participants (57.7%), 75.4% did not use condoms consistently, and 50.3% had at least 2 lifetime sexual partners. Among the study participants, the Thai studied youth had significantly higher odds of ever having had sex (AOR=2.33; 95% CI: 1.56-3.49; p<0.001), having an earlier sexual debut (AOR=5.52; 95% CI: 2.71-11.25; p<0.001) and having a larger number of lifetime sexual partners (AOR=2.31; 95% CI: 1.37-3.88; p=0.002) than non-Thai participants. There was no significant difference between the Thai and non-Thai participants in terms of having HIV testing. The Thai studied youth were more likely to engage in risky sexual behavior than the non-Thai youth. However, both groups displayed risky sexual behaviors. Future research should explore in-depth the drivers of risky sexual behaviors among both Thai and non-Thai youth.