Satisfaction with life correlates with other measures of subjective wellbeing and correlates predictably with individual characteristics and overall health. Social indicators and subjective wellbeing measures are necessary to evaluate a society and can be used to produce national indicators of happiness. This study therefore aims to help close the gap in wellbeing data for Thailand. The specific aims are to: (1) calculate the Thai PWI and domain scores using a large scale sample; (2) examine the level of life satisfaction of Thais when compared to international standards; (3) examine the Thai PWI and domains in relation to demographic, socioeconomic, and geographic characteristics. Our report derives from the findings on the Personal Wellbeing Index (PWI) in a large national cohort of Sukhothai Thammathirat Open University adult students living all over Thailand (n = 87,134). This Thai cohort had an overall PWI of 70.0 on a scale from 0 to 100 which is consistent with Western populations. The 'spirituality and religion' domain had the highest average score. 'Standard of living', 'future security' and 'achievement in life' made the largest contribution to overall 'satisfaction in life as a whole'. These domains also show a positive trend with increasing age, being married, higher income, more education, more household assets, and rural residence. The PWI will be an important tool for policymakers to understand the subjective wellbeing of population groups especially as Thailand is undergoing a political and economic transition.