Rapid socioeconomic development since the Industrial Revolution, particularly over the past fifty years in Asia, has come at the cost of environmental degradation, including declining water quality. However, the complex relationship between socioeconomic growth and water quality dynamics remains poorly understood. This study aims to clarify the spatial and temporal interactions between socioeconomic factors and water quality across five major river basins in Thailand’s Central Plain: Phetchaburi, Mae Klong, Tha Chin, Chao Phraya, and Bang Pakong. Using a comprehensive dataset from 2011 to 2018, this research integrates socioeconomic indicators – including population size and density, gross domestic product (GDP), fertilizer use and emission, and land use – with key water quality parameters. During this period, 784 km² of forestland was largely converted to agricultural use, particularly in the upper basins, leading to increased fertilizer use and emission. Meanwhile, the lower Chao Phraya River basin experienced the most significant socioeconomic growth, with population having increased by 2.8%, GDP by 6.1%, and built-up areas having expanded by 9.4%, gradually extending to the Tha Chin and Bang Pakong basins. These areas of intense socioeconomic activity exhibited notable declines in water quality, characterized by negative correlations between dissolved oxygen levels and socioeconomic factors, and positive correlations with biological oxygen demand, ammonia nitrogen, and coliform bacteria concentrations. The findings highlight the influence of local socioeconomic drivers on spatial water quality patterns, particularly in the lower reaches of rivers, which serve as a link within the land-sea continuum. Therefore, addressing coastal eutrophication and hypoxia in the Upper Gulf of Thailand requires a thorough understanding of socioeconomic development across the watersheds in the Central Plain of Thailand.