SINGAPORE (AFX-ASIA) – Oil producer PTT Exploration & Production PCL said its board has approved its planned purchase of a 15% stake in Ratchaburi Power Co (RPC) for 249.75 million baht. (US$1=39 baht) RPC plans to build a two gas-fired combined-cycle power plants, with a capacity of 700 megawatts each. The power plants, which will…