The authors examined the relationship between socioeconomic status and smoking in Thai adults. A nationally representative sample of 7858 Thais adults (18 years and older) was surveyed during 2004 to 2005. Four demographic/socioeconomic indicators were examined in logistic models: gender, education, occupational status, and annual household income. Overall, 22.2% of the participants were smokers. Men were more likely to be smokers across all age groups and regions. Compared with nonsmokers, current smokers were less educated, more likely to be employed, but had lower household income. When stratified by gender, education and job levels were strongly associated with smoking prevalence among males. A significant relationship was found between annual household income and smoking. Those who lived under the poverty line were more likely to smoke than persons who lived above the poverty line in both genders. The present study demonstrated that socioeconomic factors, especially education level and occupational class, have a strong influence on smoking behavior in Thai adults.