BackgroundNew biologic disease-modifying antirheumatic drugs (bDMARDs), targeted synthetic DMARDs (tsDMARDs) and biosimilar DMARDs (bsDMARDs) all showed greater clinical benefits in the treatment of patients with rheumatoid arthritis (RA) with high disease activity, but imposed higher costs than standard treatment. This study evaluated the cost-effectiveness of 11 alternative treatment strategies for RA patients with high disease activity whose treatment with three conventional synthetic DMARDs (csDMARDs) failed.MethodsA Markov model was constructed using a societal perspective to estimate relevant costs and health outcomes in terms of quality-adjusted life years (QALYs) for a lifetime horizon (100 years), given a 3% annual discount. Alternative treatment strategies including five bDMARDs, two tsDMARDs, and four bsDMARDs in combination with methotrexate (MTX) were compared with the standard of care (SoC), i.e., cyclosporine and azathioprine. Direct and non-medical care costs were estimated by identifying the resources used, then multiplied by the standard costing menu in the year 2022. Utility and transitional probabilities were collected in three advanced tertiary hospitals. A network meta-analysis was used to estimate the efficacy of each treatment. Lifetime cost, QALYs and an incremental cost-effectiveness ratio were calculated and compared to the cost-effectiveness threshold of 160,000 THB per QALY gained (US $4,634, where 1 USD = 34.53 THB in 2022). Probabilistic and one-way sensitivity analyses were performed to estimate parameter uncertainties.ResultsThe bDMARDs, tsDMARDs or bsDMARDs combined with MTX provided 0.09 to 0.33 QALYs gained with additional costs of 550,986 to 2,096,744 THB (US $15,957 to $60,722) compared to the SoC. The ICER ranged from 2.3 to 8.1 million THB per QALY (US $65,935 to $234,996) compared to the SoC. None of these combinations was cost-effective in the Thai context. The results were sensitive to the mortality hazard ratio of patients with high disease activity.ConclusionsCombinations of MTX with either bDMARDs, tsDMARDs or bsDMARDs were not economically attractive compared to the standard practice. However, they reduced disease activity and improved patient quality of life. The price negotiation process for these treatments must be conducted to ensure their financial value and affordability before they are included in the pharmaceutical reimbursement list.Supplementary InformationThe online version contains supplementary material available at 10.1186/s12913-023-09595-1.