Abstract: To analyze the effect of the use of factors of production on productivity of small farmers who use <8 acres of land distributed by Agricultural Land Reform Office in the North of Thailand, this research has two main objectives: to search for factors that affect the productivity of the small farmers and to study the role of knowledge management practices on the productivity of small farmers. Research results are: most farmers have primary school background (85%). They sold most of their products to middle man with prices set by buyers (80.6%). Main source of knowledge was from family members (80%). Knowledge was shared informally while they are in the field. About half of farmers still need external helps such as sufficient irrigation system and capital from the government. As indicated by estimated productivity function, significant factors comprise of labor, water, fertilizer, pesticide and knowledge management practices and the usage of fertilizer is considered to be the most important factor. Moreover, success groups of farmers that attained balance between productivity improvement and quality of life tended to practice all processes of knowledge management activities (acquiring, storing, adjusting, sharing and creating knowledge). Qualitative evidences also confirm that farming techniques, water and marketing are crucial factors for the improvement of productivity and overall income.