This thesis aims to study the rainfall forecasting for the paddy field management of rice farmers in Yasothorn. In Baan Non Yhang, Khammaed, Kudchum, Yasothorn Province, the study was conducted to verify traditional knowledge in rainfall forecasting with the close consideration of both qualitative and quantitative methods of traditional forecasting system in comparison with scientific forecasting system. The study also employed in-depth interview to scrutinize paddy field management and conservation of native rice varieties, and household survey to figure out factors affecting choices of rainfall forecasting systems. The study found that the rainfall forecasting system by local knowledge has percent deviation of 38.26, higher than the forecast system of the meteorological department with the error of 6.81 percent. Fifty-eight percent of farmers selected the forecast of the Meteorological Department, 10 percent used only forecast rainfall by wisdom and 32 percent used both types. Selection of rainfall forecasting system by local wisdom has a positive relationship with the reasons guiding farmer decision at the statistical significant level of 0.10 (P = 0.093). The reasons include, easy access, accuracy, reliability, and experiences. Selecting meteorological rainfall forecast is related positively to the amount of dry paddy fields and attitude toward the prediction of each type with the statistical significance level of 0.039 and 0.035 respectively.