Background: Traditional Thai tobacco (Nicotiana abacus L.) is known as a non-Virginia type whose mature leaf contains three to four times more nicotine than that of a Virginia type. As such, the process of Thai traditional tobacco production may lead to adverse health effects such as green tobacco sickness (GTS).Objective: To investigate the prevalence of GTS and risk factors related to GTS among Thai traditional tobacco farmers in Nan province, northern Thailand. Methods: 473 Thai traditional tobacco farmers from rural areas in Nan province were randomly selected and interviewed in person by means of questionnaires and environmental survey. Statistical analyses were used to identify potential risk factors for GTS.Results: The prevalence of GTS was 22.6% (95% CI 19.1% to 26.6%). Multivariate analysis showed various risk factors associated with GTS including gender of the farmer (ORadj 0.44, 95% CI 0.26 to 0.73), smoking (ORadj 4.36, 95% CI 1.41 to 13.47), skin rash (ORadj 0.36, 95% CI 0.19 to 0.68), wearing a wet suit (ORadj 1.91, 95% CI 1.12 to 3.23), process of curing tobacco leaves (ORadj 0.06, 95% CI 0.02 to 0.16), and watering tobacco plants (ORadj 0.42, 95% CI 0.25 to 0.72).Conclusion: The process of traditional Thai tobacco production can result in increased dermal exposure and can be considered a major risk factor for GTS. Body soaking during watering may further increase adverse health effects related to GTS.