Over the last two decades, an impressive amount of erosion research work has been carried out in northern Thailand, but farmers' adoption of recommended erosion control measures is still very limited. A multiscale and interdisciplinary on-farm approach to erosion research was designed and tested in the context of an Akha village in Chiang Rai Province, upper northern Thailand. The selected methodology articulates complementary diagnostic analyses of erosion processes at field, farm and catchment levels. At field level, causal relationships between physiographic, climatic and agronomic practices across diverse on-farm situations are presented and generate a series of key thresholds for decision making purposes. Results of on-farm assessment of introduced and indigenous soil and water conservation practices are also shown. At catchment level, the emphasis is on understanding the spatial distribution of major erosion damage. The key role played by contour convexities and rural infrastructure is underlined. At farm level, different farmers' strategies and related erosion risks are first identified, and the way to use the farmer typology tool to target better and to improve the efficiency of soil and water conservation efforts is discussed. Finally, a critical evaluation of such an integrated erosion survey is made.