Based on the economically and socially statistical data during the year 1989 - 2001,Thailand has suffered flood and drought periodically and the amount of damages sometimes was higher than 70,000 million baht or 23,700 million baht on average. Therefore, the Royal Thai Government - RTG considers that is a seriously threat to the national development and is a significantly obstacle to the quality of life. Furthermore, water issue is very much interrelated with other natural resources such as forestry, land, ecosystem, etc. as well as human settlement which has an impact on the economic growth. As stated in the Johannesburg Plan, the Integrated Water Resources Management – IWRM is one of the perfect tools that should be applied in order to minimize the obnoxious problems. So, the IWRM approach of which is adopted in Thailand should be further applied in the 25 river basins in the country. Moreover the RTG’s policies on water resource management, the solutions for development or rehabilitation will be verified and presented into three main categories based on area functions which are the upper (forest area), middle (agricultural area and community), and lower (downstream included coastal area) River Basin. An update information concerning all natural resources and other related maters included an environmental aspects shall be examined, monitored and technically verified for database establishment, to generate management and other plans in the most effective and proper processes from the upper through lower downstream areas