Hydrological data procurement in Thailand was stated in 1831 for the purpose of predicting the agricultural production. The work had been originated and confined in the lower delta area and gradually moved toward headwater. Systematic investigation and scientific methods have been introduced since 1905 due to the need of water resources development. The inaccessibility caused by geographic and underdevelopment conditions of the area prevent an appreciable progress of the undertaking. The concept of the investment in hydrologic data procurement in relation to the degree of water resources development is always kept in view. Hard friction has been found in conducting the works in such the remote river-basin areas, such as observation, communication, transmission, techniques of procurement and processing of data. These factors create difficulties in hydrologic assessment for appraisal of water resources development projects. Consequently, indirect approaches have been enforced to play a predominant role in the area. Therefore, in order to overcome these difficulties, the promotion of regions research activities as well as modified methods of analysis of regional problems is immediately required. It is obvious that the establishment of master plan is desirable to help institutes the actual program for hydrologic investigation, to help assist in locating the problems, and to avoid the collection of unnecessary data