Background Illicit cigarette consumption has increased worldwide. It is important to understand this problem thoroughly.

Objectives To investigate behaviours and factors associated with illicit cigarette consumption in southern Thailand.

Design A survey and qualitative study were conducted in a border province in southern Thailand next to Malaysia. A modified snowballing technique was used to recruit 300 illicit and 150 non-illicit cigarette smokers. A questionnaire was used to interview subjects. Illicit cigarette packs were obtained in order to identify their characteristics. Bivariate and multivariate logistic regression was used for data analysis.

Results Smoking of illicit cigarettes has become accepted in the communities. They were available in supermarkets and vendor shops. Friends and other illicit smokers known by illicit cigarette smokers were an important source of information for access to illicit cigarette products. The main factors associated with smoking illicit cigarettes, compared with smoking non-illicit cigarettes, were younger age, higher education and higher average monthly expenditure on cigarettes (most illicit smokers smoked illicit cigarettes (average price per packet = 33 THB (US$1.1), while most non-illicit smokers smoked hand-rolled cigarettes (average price per packet = 7 THB (US$0.2)) and knowledge of other illicit cigarette smokers. The low price of illicit cigarettes was the main reason for their use. Selling strategies included sale of singles, sale in shops and direct sale through social networking.

Conclusions Illicit cigarette consumption has become more acceptable especially among young adult smokers. Age and extent of social networks are important factors associated with smoking illicit cigarettes.