The chapter aims to compare the effect of different types of small-scale irrigation on: crop production and farm income, water allocation and project maintenance, the level of farmer participation in water user organizations (WUO), and the economic efficiency of project investments. The northeast region is the poorest among the regions in Thailand. The major portion of farm land is devoted to rice production and yields are the lowest in the nation. Because of the situation the Thai government has invested in several large-scale irrigation projects in the northeast. The purpose of the small-scale projects is to meet the "basic requirements" of the population, defined as the basic subsistence requirements for domestic water needs, for minimal supplementary irrigation, and for minimal dry season irrigation of garden plots. One of the serious problems associated with the projects is the lack of effective and efficient utilization of water. Associated with this inefficient utilization is the absence of viable WUO.