UPDATE 1-Thai PTTEP cancels swap of Myanmar stakes with CNOOC

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BANGKOK Feb 25 (Reuters) - Thailand's PTT Exploration and Production PCL PTTE.BK said on Wednesday it had cancelled a deal to swap stakes in Myanmar's offshore M3 and M4 blocks for Chinese energy giant CNOOC's (0883.HK) A4 and C1.

The contract for the swap had expired before approval was won from Myanmar's government, so it became invalid, PTTEP said in a statement to the exchange.

PTTEP International, an operator of oil and gas fields in army-ruled Myanmar, will maintain its 100 percent holding in blocks M3 and M4.

The company had signed a deal with CNOOC Myanmar Ltd last April, hoping to swap its 20 percent stake in offshore gas blocks M3 and M4 to the Chinese firm in exchange for a 20 percent share of CNOOC's A4 and C1 blocks.

Blocks M3 and M4 in the Gulf of Martaban off Myanmar have strong gas potential.

Block A4 is a gas field located off the former Burma's Rakhine coast, while C1 is a potential onshore oil field.

PTTEP, a subsidiary of PTT PTT.BK, Thailand's top energy firm, has been aggressive in buying new gas and oil assets at home and abroad to increase reserves and capacity to meet rising domestic demand.

PTTEP also owns 100 percent of offshore block M9, which is still under exploration in the Gulf of Martaban, south of Yangon, Myanmar's main city.

At the midday break, PTTEP shares were up 1.12 percent at 90 baht while the main index .SETI was up 0.57 percent. ($1 = 35.65 Baht) (Reporting by Ploy Chitsomboon; Editing by Alan Raybould)