Yes it is a huge investment, but it is safe energy for 50, they speak already about 80 years on the new plants. And all the world is building them. Poland alone is planning 6 new nuclear power plants to replace their coal plants. Since a long time the spent fuel rods can be recycled it is not the 1980s anymore. It is by far the cheapest source of electric and it produces almost no CO2.
We can't increase electric consumption (Aircons, electric cars), don't build power plants, close coal power plants and complain about increasing prices. Either prices are high so industry goes into other countries and normal people can't have airconditions, or we build coal power plants (I don't know if Thailand has coal domestic) or we build nuclear power plants. Only problem is that no one want to have it close to their land. I wouldn't want it in my neighborhood. But I wouldn't want a coal power plant in my neighborhood as well.