This study reports the results of the second wave of a prospective study of adult smokers. The study is being carried out as part of the project ‘International Tobacco Control Policies Survey:- Southeast Asia (Thailand) (ITC-SEA). The study has three major objectives: 1) explore smoking behavior, knowledge of, and attitudes to, smoking, and knowledge of tobacco policies; 2) analyze the individual and environmental determinants of smoking behavior, and 3) evaluate the effects of tobacco control policies on smoking behavior. In this report we focus on comparing the results from Wave 1 and Wave 2 of the study.