Salinization is common in Northeast Thailand and it hampers the activities of farmers. Characteristics and countermeasures are described at 2 levels: local and watershed levels. In the latter, salinization is controlled based on topography, geological strata and groundwater. In the former, salinization is closely related to the movement of water in and on the soil. Cheap, simple, effective and economical countermeasures including “core techniques” at the local level were developed for the farmers. A countermeasure with long-lasting effects at the watershed level was proposed to the government for completing the amelioration in cooperation with the farmers.