In Thailand, according to the Power Development Plan (PDP 2007), during the year 2007-2021, the government of Thailand plan to have the most economic power generation resources yet reliable and least environmental impact. At the present time, in addition, the emerging energy crisis resulting from an uncertainty price of crude-oil and the emerging global warming crisis results from carbon dioxide emission have drawn an attention about renewable energy all over the world including Thailand [1-2].One of the most effective solutions for Thailand is to promote the renewable energy usage in the rural area especially from solar energy and wind generation system. However, with the fast growing in wind power technologies, many concerns and focuses pay to this type of renewable energy in the country. Unfortunately, Thailand is considered as a country of low to medium wind speed profile with approximately wind capacity factor close to 30 percent. Therefore, in order to obtain the most efficient and effective wind generation system for rural household usage, the optimal design for a household scale wind generation should be governmentally supported and implemented. This paper, therefore, addresses to this issue and study result shows that the optimal scale of household wind generation system is 5 kW. with a proposed cut-in speed at 2.5 m/s while the suggested rated power at wind speed of 8 m/s. This proposed wind generation system can offer an Optimal Annual Capacity Factor (OACF) close to 30 percent.