The investment, estimated at Bt6.9 billion, will be carried out by its 80-per cent-owned subsidiary, Ratch-Australia.
In a statement, the company said that the solar farm will replace Collinsville coal-fired station which was shut down last June.
According to Pongdith Potchana, chief executive office of Ratch, the 23 megawatt Collinsville Solar PV has been granted development license and proceeding selection of engineering procurement contractor. It plans to operate commercially in 2015.
The 30 megawatt Collinsville Solar Thermal has received A$2.5 million or Bt75 million financial support from the Australian government to conduct feasibility study and expects additional subsidy from the government to make it commercial worthiness and become a prototype of solar thermal technology in Australia. The project development will start in 2015, for commercial operation in 2017.
"Australia is a potential market where the company sees more investment opportunities particularly in renewable segment - wind and solar power. This is because the Australian government's aim to increase electricity capacity from wind and solar power sources to 20 per cent of total capacity in 2020," said Pongdith.
The investment will increase the Australian subsidiary's capacity to 870MW and Ratch’s renewable capacity to 209MW representing 3.3 per cent of its total 6,303MW capacity.