This paper studies the possibility of power generation by using alternative energy in Thailand which are geothermal energy, solar energy and waste energy based on the energy and economy indicators. An Organic Rankine Cycle (ORC) is used to generate electricity from heat sources of hot springs, solar water heating system and RDF-5, respectively. In this study, a 20 kW ORC system with using R-245fa as working fluid was tested and evaluated the system efficiency. It could be found that the efficiency of ORC system was around 8%, when hot water temperature was higher than 100 ºC. The values of levelized electricity costs (LEC) of geothermal energy, solar energy and waste energy were 0.148, 0.547 and 0.442 USD/kWh, respectively. The suitable alternative energy for generating electricity was the geothermal energy which was beneficial than the solar and waste energy power plants in terms of energy and economy results.