This paper reviews the possible linkage between population factors such as population size/growth, in-migration/out-migration, and age/sex structures and land degradation in northeastern Thailand. Using both qualitative and quantitative methods, the feasible relationship between population factors and land degradation are analyzed. In addition, a review of the existing reforestation and population policy of the Thai government is presented. Analysis within sample units demonstrated a significant relationship between land degradation and population dynamics and economic factors. The sample analyses showed that the rate of change was influenced by environmental conditions, which play an important role in the man-forest interaction. Based on the findings, four concluding remarks are drawn. These include: 1) population growth usually appears as the major cause for land degradation; 2) overgrazing, and especially cassava growing in the northeast, have destroyed vegetation which led to the loss of topsoil; 3) the promotion of mono-cash crops by the government increased land clearing for cultivation in the northeast both for the domestic market and for export; and 4) population factors are viewed as an intermediate variable; social variables such as agricultural technology, fertilizer, irrigation, economic factors are influenced by population growth which exacerbates the effect of these processes.