Wind energy potential analysis is a design key to maximize wind turbine efficiency and annual energy output. Typically, the annual wind speed frequency is represented by a Single-Weibull distribution curve in spite of strong and calm wind patterns could occur through a year in many regions in the world, Thailand for instance. For this reason, wind energy potential should be analyzed by Multiple-Weibull distribution curves which are the representative of the meteorological seasons due to the monsoon’s effect. Therefore the objective of this study is to compare the accuracy of the Single-Weibull distribution and the Multiple-Weibull distribution in assessment of wind energy potential. The comparison was made between these two statistical distribution functions and the actual wind speed distribution (measured wind speed frequency) in order to determine the level of credibility of these two distribution functions. The wind speed data employed in this study was measured at Lamtakhong dam site in Nakhon Ratchasima province, Thailand. As the results, the error between the Single-Weibull distribution was 16.46% where the error between the Multiple-Weibull distribution was 14.82%, it was revealed that the smaller error, the higher reliability. Two of the most widely used wind turbines (Enercon E-30 and Windspot) were selected to verify the Multiple-Weibull concept. Approximately 40% increase in annual energy yield by using this method. So, the results confirmed that the Multiple-Weibull distribution is valid for the assessment of the annual energy production of wind turbines. Therefore, this will be a practical method for achieving the optimal design of stall-regulated wind turbine in the further work.