Rice is annually destroyed by seasonal flooding in South and Southeast Asia. In order to reduce the loss of rice production, an accurate assessment of flood-affected paddies is essential. Taking the 2001 monsoon flooding that hit the Lower Chi River Basin, northeastern Thailand, as a case study, we derived the flood depth over the large and inaccessible areas using a RADARSAT-1 image acquired during the flooding peak and a 30-m Digital Elevation Model. Based on the elongation properties of rice, we used the critical water-depth of 80 cm to classify the flood-affected paddies into ‘damaged’ or ‘non-damaged’ paddies. Our results show that only about 40% of the flood-affected paddies were actually damaged paddies. In addition, we analyzed the damaged paddies by overlaying the derived water depth with the flood frequency map in order to recommend planting the appropriate rice varieties. Our analysis reveals that remote sensing and GIS can be used to minimize the loss of rice production and thus help farmers to increase their income in the long run, which will save the government money paid in flood compensations.