Main season rice-based cropping systems in Thailand are sensitive to the influence of climatic characteristics and patterns, which are induced by global warming. Despite uncertainties regards the precise magnitude of climate change projection at high resolution at regional scales as well as the timescales which are far into the future, an assessment of the possible impacts on our agricultural resources is important in formulating an adaptive response for rice production strategies. In the present study, CropDSS shell was used to link the CSM-CERES-Rice model version 4.0.2.0 with future climate scenarios from the PRECIS regional climate model (RCM) to downscale the ECHAM4 Global Climate Model (GCM) for Thailand. Data obtained from the ECHAM4 GCM under SRES A2 and B2 GHG emission scenarios were downscaled to higher resolution to project climate scenarios for the period 1980-2099. A slight decline in main season rice yields was predicted under all production systems before the 2040 period with a drastic decline in yield after the 2040 period. However, one should also bear in mind the predicted amount of rainfall and the relationship of more incidents of insect pests. The CropDSS shell and the CSM-CERES-rice model may be used to evaluate alternative adaptive production strategies under future climate scenarios projected by the ECHAM4 GCM in Thailand and other countries, providing that datasets are available for model testing and evaluation.