There are numerous water resource development projects in the Nam Kam River Basin of Nakhon Phanom province in the northeastern part of Thailand. The Nam Kam River Basin is one of the Greater Mekong’s tributaries and covers an area of approximately 3,440 square kilometers. The operation of the development projects situated along the basin must be in a manner that avoids salt solution diffusing into the nearby areas and protects the existing irrigation systems and reservoirs from large amounts of salt seepage. Since saline soil, salt crusts and ancient land salt pits have been found on the ground surface of the Nam Kam Basin, the purpose of this research is to investigate the saline areas by interpreting the satellite images. The interpreted satellite images were mapped and the results were validated against the actual field data. The salinity of soil and water was measured by the electrical conductivity meter and laboratory testing. The preliminary investigation of the study area showed two groups of the saline areas: saline soil spots and ancient land salt pits. Certain difficulties remained in the interpretation of the satellite images, such as the inability to classify the degree of salinity with accuracy and the outdated data in the areas with human involvement. The saline soil spots occupied by landowners are mostly improved for agriculture; on the contrary, the ancient land salt pits are operated only by a few villagers during the summer. Even though in summer 2012, the local office of Royal Irrigation Department flooded the ancient salt pits to protect them from salt farming, the villagers continue producing salt, thereby causing salinity to spread more widely. The study reveals that monitoring of salinity of the water and soil is necessary and is currently carried out jointly by academics, the local community, and agencies responsible for the irrigation projects in the study area.