* Q3 profit 36.1 bln baht vs forecast 34.6 bln baht
* Revenue up 5.8 pct, gas sales hit record
* Shares underperform market this year
By Khettiya Jittapong
BANGKOK, Nov 14 (Reuters) - PTT Pcl, Thailand's top energy firm, posted its biggest rise in quarterly net profit in more than a year, boosted by robust gas sales, higher income from its upstream unit, and rising profits from its refinery and petrochemical businesses.
PTT's gas sales hit a quarterly record in July-September due to Thailand's rising demand for the fuel. Asia-Pacific's third-biggest oil and gas firm by market value is likely to enjoy strong earnings growth next year, with analysts forecasting a 4-6 percent rise in gas demand over the next two years.
State-controlled PTT posted July-September net profit of 36.1 billion baht ($1.2 billion), up 68 percent from a revised 21.47 billion a year earlier, and higher than the average 34.6 billion baht forecast by 11 analysts polled by Reuters.
The profit growth was the highest since the second quarter of 2011 when it posted a 91 percent rise.
PTT's third-quarter revenue climbed 5.8 percent from a year earlier to 686 billion baht, with gas sales rising to a record 4.611 billion cubic feet per day, up 8.5 percent on year.
Increased demand for gas in Thailand has prompted PTT to secure more supplies from domestic and regional fields, including Myanmar, and beyond to Africa and the Gulf.
A company official told Reuters this month that PTT is looking to invest heavily in energy assets in Myanmar, excluding acquisitions, through 2020 as the country opens up after decades of military rule. It is also eyeing investments in the power business in Laos.
PTT has also unveiled plans to buy liquefied natural gas from Qatar Liquefied Gas Company Limited from 2015, and last month won approval to build the second phase of an LNG receiving terminal.
The company's upstream unit, PTT Exploration and Production (PTTEP), saw its third-quarter net profit more than double, mainly due to higher sales volumes and rising prices.
PTTEP is looking to Mozambique-focused gas explorer Cove Energy, acquired this year, to help meet increased gas and energy needs.
PTT, valued at around $30 billion, runs Thailand's gas pipeline monopoly and controls more than 30 petroleum, gas exploration, petrochemical and refinery businesses.
Its shares have edged down 0.3 percent so far this year, underperforming a 26 percent gain for the broader market on concerns about the global economy and losses from fuel subsidies for natural gas for vehicles (NGV).
Before the earnings announcement, the company's stock closed down 0.94 percent on Wednesday, in line with a 0.76 percent drop in Bangkok's main index.
PTT ranks behind PetroChina and Sinopec in market value among oil and gas companies in Asia. Its latest report outshone both PetroChina, which posted a 33 percent fall in third-quarter profit, and Sinopec's 9.4 percent drop in earnings.
But seasonal low gas sales and lower profits from affiliates could drag down PTT's fourth-quarter earnings, analysts have said.
Eager to secure resources to feed rising domestic and regional demand for energy, PTT has been aggressive on the M&A front this year, but next year the company will focus on developing existing assets, Chief Financial Officer Surong Bulakul told Reuters this month.
$1=30.65 Baht Editing by Jeremy Laurence and Mark Potter