The above figure shows an average value of solar irradiation in several areas in the world. The largest potentials we find in Northern Africa and on the Arabian Peninsula, as well as in South Africa and Australia. And also the values of Spain and Southeast Asia are recommending solar thermal power plants. The global solar irradiation in Thailand is between 1700 and 1900 kWh/m2-a. If considering direct radiation, which is essential for solar thermal power plants, has an average percentage of 52 % of the global radiation under the tropical climate conditions of Thailand [2], than 850 and 950 kWh/m2-a are an effective potential. Cloud coverage impact is an important issue and needs to be considered while choosing a suitable site. Some areas in Thailand can not provide enough stable weather conditions to create a constant electricity production with CSP / steam turbine configurations.