This research analysis of flood risk areas. A case study of the Chao Phraya watershed district The analysis is intended to find an area vulnerable to flooding occurred. Factors analyzed in this research have the 9 factors: rainfall flooded areas in the past. Slope of the area. The height of the terrain. The size of the drainage basin area, the density of River Sub-the density of communications routes and land utilization. The analysis process relies on a process, the weighted values for each factor, and the overlap of the data area of layer. The results caused a flood risk area has been divided into four levels of risk areas, the risk is high level intermediate risk level areas, areas and areas where there is no risk of flooding occurred. The results showed that the County watershed, we are vulnerable to extreme levels, flooding occurs. About 9027 square kilometers or about 44.55% of the Chao Phraya watershed zones area. Information from the analysis are presented as reports and maps. In order to have preliminary information on support and surveillance in areas vulnerable to flooding.