Objective: To assess annual direct and indirect costs in a prospective cohort of patients with rheumatoid arthritis (RA) in Thailand from the societal perspective.  Methods: Data on costs and intangible losses were prospectively collected at regular intervals over a one-year period from 158 RA patients who attended a major tertiary care facility in Bangkok, Thailand. Direct medical, direct nonmedical, indirect, and total costs were estimated according to patients’ respective health insurance conditions and converted to 2001 US dollars using published purchasing power parity estimates. Sensitivity analyses were performed and the predictors of costs and intangible losses were investigated.   Results: The average societal cost of RA was estimated to be US$2682. 41.4% of patients’ average annual income. Average direct and indirect costs were estimated to amount to US$2135 and US$547 per patient per year, respectively.  Seventy-three patients (46.2%) experienced at least one event of intangible losses and 46 patients (29.1%) had decreased earning ability because of RA.  Poor physical function, joint deformity, high number of disease modifying antirheumatic drugs, and steroid use contributed to higher costs and presence of intangible losses.  Conclusion: RA consumes a significant proportion of patients’ annual average incomes and poses a significant economic burden to society. Since RA mainly affects a working-age population, early and timely treatment of this disease can improve both the suffering and the economic productivity of patients in Thailand.