PTTEP will sell 650 million shares at 142 baht ($4.62) in Asia's biggest rights issue so far this year and Thailand's biggest ever secondary offering. PTTEP had set a price fork of Bht135 to Bht145, a range that analysts said was below their expectations.

"The final offering price reflects current market demand for PTTEP's newly issued ordinary shares," PTTEP President and CEO Tevin Vonganich said in a statement. "The equity raising will enable PTTEP to strengthen its capital structure and allow the company to achieve its growth plans."

PTTEP has been a regular buyer of overseas assets in recent years after the Thai state, which owns 65% of PTTEP through PTT PCL, pushed the company to expand its overseas holdings to secure reserves for domestic use.

In July PTTEP paid £1.22 billion ($1.9 billion) for Cove Energy plc, a London-listed, Mozambique-focused gas prospector, after outbidding Royal Dutch Shell plc. In 2010, PTTEP paid Norway's Statoil ASA $2.28 billion for a 40% stake in the Canadian Kai Kos Dehseh Oil Sands Project. PTTEP said it plans to produce about 900,000 barells of oil equivalent per day by 2020 and spend about $20 billion by 2016 to achieve that goal.

Existing shareholder have a preferential right to buy the new shares at a rate of 0.195783 of a new share per existing share. PTT has said it will take up its full entitlement.

Subscriptions to the share sale will run from Dec. 3 to Dec. 6. The new shares are expected to begin trading on Dec. 14.

PTTEP has tapped Bank of America Merrill Lynch, Deutsche Bank AG, Goldman Sachs Group Inc., JPMorgan Chase & Co. and UBS to act as international book runners and lead managers. Its domestic book runners are Phatra Securities Pcl, Tisco Securities Co. Ltd. and Finansa PCL.

PTTEP shares traded Friday on the Bangkok exchange at Bht159, up Bht5, or 3.3% on their Thursday close.