Soil moisture, soil strength, and other relevant data were collected in Thailand during two wet seasons and one dry season for use in the development of methods to predict soil trafficability for off-road ground contact vehicles in Southeast Asia. Data were collected at 75 test sites distributed in eight geographic areas which had differences in soils, weather regimes, terrain, and land use. From data collected monthly at the 75 sites, specific soil strength-moisture relations were derived to depict the changes in strength that corresponded to changes in moisture content. From data collected daily at 17 sites, specific soil moisture prediction relations were derived following procedures developed for sites in the United States. Results showed that the prediction methods were applicable to Thailand sites that were well drained. Modifications in the methods should be developed to account for the influence of water tables when present. Similarities in specific prediction relations between Thailand and the western hemisphere indicated that the development of average prediction relations is feasible. Descriptions of Thailand and study areas are given in Appendix A. An application of the Thailand data, the derivation of a general soil moisture map for South Vietnam, is given in Appendix B. The basic data are summarized in Volume 2. (Author).