Abstract Background There is limited evidence on the association between oral health and general health in middle-income countries. This study analysed data from 60,569 adult students enrolled at Sukhothai Thammathirat Open University and residing throughout Thailand who reported oral health impacts at the 2005 baseline and 2009 health status based on Short Form (SF-8) survey. Findings In 2005, 16.4% had difficulty chewing and/or swallowing, 13.4% reported difficulty speaking and/or discomfort with social interaction, and 10.8% of the cohort reported having pain associated with teeth or dentures. Cohort members reporting one or more oral health impacts in 2005 had lower SF-8 mean scores in 2009. In particular, monotonic dose–response gradients in 2005–2009 associations based on multivariate linear regression were found between an increase in number of oral impacts (0, 1, 2, 3) and a decline in SF-8 Physical Component Summary scores (adjusted means of 50.5, 49.2, 48.6, 47.9) as well as SF-8 Mental Component Summary scores (adjusted means of 43.2, 40.9, 40.3, 38.6) in younger cohort members. Similar dose response gradients were found in older cohort members. Conclusions We found strong association between oral health impacts and adverse health and quality of life among Thai adults. This finding confirms that oral health is one of the key determinants of population health.