The aim of this study was to estimate the prevalence and identify associations between suicidal ideation and indicators of psychosocial distress and social-environmental factors in Thai adolescents. Using data from the Thailand Global School-Based Student Health Survey (GSHS) 2008, we assessed the prevalence of suicidal ideation and its associated factors among adolescents (N = 2,758). Overall the prevalence of suicidal ideation in the past 12 months was 8.8% (9.9% males and 7.7% females). Variables influenced the suicidal ideation in multivariable analysis were sadness (Odds Ratio = OR: 6.03; 95% Confidence Interval = CI (3.00–12.14), lack of parental attachment (OR = 2.26, CI = 1.09–4.67), current alcohol use (OR = 2.32, 1.21–4.44), and ever having had sexual intercourse (OR = 4.16, CI = 3.40–7.68). Psychosocial, health-risk behaviours and lack of protective factors appear to effect suicidal ideation in this youth population.