INTRODUCTION To prevent youth from becoming smokers, it is essential to understand factors contributing to them becoming susceptible to smoking. The aim of this study was thus to estimate the prevalence of smoking susceptibility among neversmoking youth in Thailand and to identify determinants associated with such behavior. METHODS Cross-sectional data for 4572 eighth-grade students (aged 13-15 years) from 120 secondary schools were obtained from a classroom-based survey using a self-administered questionnaire. Using data from never-smoking students (n=3180), simple and multiple logistic regression analyses were performed to identify factors associated with smoking susceptibility. Frequencies and proportions for descriptive statistics are reported along with adjusted odds ratios and 95% confidence intervals for logistic regression models. RESULTS A total of 16.4% of Thai never-smoking youth were susceptible to smoking. Several variables of interest were identified in multivariable analysis as significantly associated with increased susceptibility to smoking: being male (AOR=3.16; 95% CI: 25.4-3.92), having a positive attitude toward smoking -agreeing that smoking displays maturity (AOR=1.49; 95% CI: 1.07-2.09), the perception that smoking helps relieve stress (AOR=1.57; 95% CI: 1.14-2.15), the presence of current smoking peers (AOR=2.04; 95% CI: 1.57-2.66), exposure to secondhand smoking in public (AOR=1.51; 95% CI: 1.17-1.94), exposure to online cigarette and smoking-related advertising occasionally (AOR=1.98; 95% CI: 1.49-2.65), attendance at schools where there are sometimes anti-smoking education activities (AOR=1.57; 95% CI: 1.18-2.07); as well as exposure to anti-tobacco messages rarely (AOR=1.40; 95% CI: 1.05-1.87), occasionally (AOR=1.48; 95% CI: 1.12-1.96) and infrequently (AOR=1.41; 95% CI: 1.07-1.87). CONCLUSIONS Approximately one in six Thai never-smoking youth was found to be susceptible to smoking. Findings suggest it should be useful to supplement relevant tobacco prevention and control efforts by considering such interpersonal and socio-environmental determinants, among vulnerable people to smoke.