[Objective] The objectives of this paper were to review and synthesizes the research programs which were conducted in the field of change of forest vegetation and the evolution of soil erosion in Southeast Asia, and to discuss the effectiveness of improved conservation practices on managing soil erosion and sediment yield at catchment scale.[Methods] The forest vegetation change countermeasures at different spatial and temporal scales were analyzed according to data from countries in Southeast Asia. This paper focused on an extensive range of methodologies at different spatial and temporal scales. The research area was the region selected for the implementation of watershed management in Thailand. The efficacy and practicality of passive and active erosion control strategies were expounded.[Results] ① Forest loss in Southeast Asia had remained at high levels during the period from 2000 to 2005, accumulating to an annual deforestation rate of about 2.76×10⁶ ha. However, forest cover has increased in the recent years due to the establishment of forest plantations. ② Southeast Asian haze was a large-scale air pollution problem that occurs regularly. The haze was largely caused by illegal agricultural fires. ③ Soil erosion control strategies for manage soil erosion in Southeast Asia include alley cropping, contouring, strip cropping, grass barriers, conservation tillage, minimum tillage and hedgerow inter-cropping. Despite the role of conservation practices being well established in reducing water runoff at the plot scale, extrapolation to a large scale, it has been less understood and verified. The potential impact of soil conservation on yield may be a key factor that affects the value of soil conservation investments.[Conclusion] The challenge of forest vegetation change in Southeast Asia is real and urgent. Regional prevention and control mechanisms should be constructed to decrease forest fire and haze. To decrease soil erosion, we should keep a sustainable forestry and sustain terrestrial biodiversity. Selection of appropriate soil conservation methods for low income smallholder farmers is critical to reduce the rate of soil erosion as well as to increase crop productivity.