<p>Thailand, a key contributor to regional and global food supply, faces intensifying hydroclimatic challenges driven by rising temperatures, shifting monsoon patterns, and increasing rainfall variability. While future climate projections indicate that terrestrial water storage (TWS) may increase over large parts of the country due to enhanced precipitation, this hydrological gain does not necessarily translate into improved agricultural productivity. This study integrates high-resolution, bias-corrected climate projections under two emissions scenarios (SSP2-4.5 and SSP5-8.5) with water and crop simulations to assess the impacts of future climate change on TWS and the suitability, yield potential, and water demand of four economically significant crops—rice, maize, sugarcane, and cassava—across Thailand. By explicitly coupling hydrological storage dynamics with crop suitability modeling, the results reveal a spatial and temporal decoupling between TWS and crop performance: although rainfall and TWS are projected to increase in most regions, especially in the south, rising temperatures amplify evapotranspiration and heat stress, significantly reducing yield potential in temperature-sensitive crops such as rice and sugarcane. Under SSP5-8.5, rice yield declines by up to 10%, and sugarcane by up to 50% under modeled potential conditions, particularly in the central plains and northeast. In contrast, maize and cassava exhibit greater resilience, with moderate or localized impacts on yield. The findings highlight that climate-induced changes in crop calendars, growing periods, and thermal thresholds play a critical role in shaping future agricultural performance, beyond TWS alone. This study highlights the importance of climate-resilient water management, crop diversification, and the development of heat-tolerant cultivars to ensure Thailand’s food security in a warming world.</p>