Objective: To determine factors predicting smoking behavior through multilevel interventions in the Royal Thai Army Conscripts.
Material and Method: The present study was a part of quasi-experimental research designed to evaluate the effectiveness of smoking cessation program based on ecological model for improving smoking behavior among the conscripts in the three levels of behavior change interventions; intrapersonal level, interpersonal level and organizational level. The 89 participants were purposively selected from the first infantry regiment of conscripts who were current smokers from the King’s Royal Guards recruited into the Army in the first section of the year 2009 and put into a trial run-through of the three influential factors process throughout the first six months. The instruments used to collect data was a self-administered questionnaire used between May 2009 and November 2009. In addition, the individual interviews and checklists of observations were employed to collect data related to organizational intervention. Data mining classification was used to predict the influential factors improving smoking behavior after the end of smoking cessation program at six months.
Results: The conscripts were able to change their smoking behaviors. 62.9% of participants reduced smoking, and 4.5% could quit smoking. Data mining analysis showed self-efficacy in intrapersonal level was the crucial variable to predict smoking behavior which correctly classified in the model 77.78%, subsequently, behavioral factors, e.g., duration of smoking and the number of cigarettes smoked per day. Additionally, organizational intervention also had an influence on the change of smoking behavior by strengthening the policy related to tobacco control, setting smoke free workplace and supporting from the commander. For interpersonal intervention, family support alone did not improve their smoking behaviors.
Conclusion: Self-efficacy and organizational intervention can help the conscripts improve their smoking behaviors during service in the army.

Keywords: Predicting factors, Smoking behavior, Multilevel interventions, Conscripts