Thailand may experiencing The Dark World within 12 years in the future as the UK has revealed that could be found Crisis of Dark World after power not enough for The entire country in this Winter.[1] Thailand has to plan Thailands power capacity development within The National Energy Policy Committee (NEPC) The Cabinet in June 2007 assigned to the Ministry of Energy. Then Energy Policy and Planning Office (EPPO) and Electricity Generating Authority of Thailand (EGAT) have to plan Thailands power capacity development known as PDP 2007(Power Development Plan) Since 2007-2021 .Then first thing should take to forecast a shortage of power in Thailand. The Research found that Thailand may experiencing fuel shortages that will bring electricity such as Natural Gas in Gulf of Thailand will run out within 20 years Oil prices higher deterioration of the power plant about 5 plants. Current energy sources used to produce electricity to most of Thailand about. 66.19% of energy from natural gas remaining list is lignite approximately 12.60% coal 8.39% water energy 5.43% bought for 3.06% furnace oil 2.66% renewable energy 1.64% diesel oil 0.03% [2] The forecast demand of electricity since 2008-2021 is found since 2016 get start problem about Thailands capacity to produce electricity is 44562.8 MW but domestic demand is 44585.40 MW that mean capacity of energy is not enough for demand that lack approximately 295.6 MW. Thailand has to consider fuel source to bring electricity what be produced at lower costs to compete in international markets such as nuclear power plants etc.