Global climate models of CMIP6 were used to project rainfall data for the future period 2023–2100. The global climate model outputs from CMIP6 and ScenarioMIP experiments were obtained from the Earth System Grid Federation (ESGF) via https://esgf-node.llnl.gov/projects/cmip6/. Lawin et al. (2019) recommended using a multi-model ensemble approach to improve the robustness of future climate projections. Therefore, in this study, the results of five GCMs from CMIP6 were selected from the top three GCM efficacy rankings for mainland Southeast Asia and Thailand according to Iqbal et al. (2021) and Khadka et al. (2022), as summarised in Table 2. Daily precipitation (pr) of the GCM outcomes was examined to assess the impact of climate change across the PRB under historical and future scenarios. The 30-year historical period from 1985 to 2014 was defined as the baseline. For the future period from 2023 to 2100, two Shared Socioeconomic Pathways, SSP2-4.5 and SSP5-8.5, were considered in relation to the regional changes to assess the potential impacts of climate change in the 21st century. The future period was divided into three timeframes: near (2023–2048), mid (2049–2074), and far-future (2075–2100). The SSP2-4.5 scenario represents the moderate forcing level with non-extreme land use and aerosol pathways, whereas the SSP5-8.5 scenario exhibits the highest emission, capable of generating a forcing level of 8.5 W/m² in 2100.