The state-owned Petroleum Authority of Thailand (PTT) aims to broaden its base by the end of the decade and spread its operations into other countries in Asia, company and trade sources said on Monday.

''Within the first 10 years of our establishment, PTT has transformed

from a government company to a national oil firm. Now we are trying to become a regional oil company," a high-ranking PTT executive in Bangkok said in a telephone interview."Hopefully, by the end of this year, a lot of these concepts will materialize," said Don Wasantapruek, PTT's Singapore representative. "A lot depends on the new government and how they'll approve PTT's spending."

PTT was originally established by the Thai government to ensure national energy stability.

It is involved in virtually every aspect of the Thai petroleum industry,

from exploration and production to refining and retail marketing of petroleum products.

PTT holds 36 to 38 percent of the Thai domestic market share, including fuel-oil supplies to power plants.

"We believe our survival is through retail operations and backward integration. Our experience in service-oriented industry would give us a competitive edge or at least put us on equal footing with international players," the Bangkok executive said.

He added that this was a feasible direction since PTT cannot compete on capital or personnel in the international arena in the same way as Shell or Caltex.

In recent years, the state company has spread its tentacles. It has established retail gasoline and liquid-petroleum-gas markets in China,

Vietnam, Cambodia, Laos, Burma and its latest target, the Philippines.

Business associates of PTT have noted the company's enthusiasm to enter the Philippines, hinting of its ambition to open 500 gasoline stations in the country. In the Philippines, Caltex has the most gasoline stations with 1,045, followed by Shell Philippines with 876 and Petron with 842.

"Our move there depends on the investment environment," the Bangkok PTT executive said, but he declined to give details. "Everything is under conceptualization, and the concepts for the projects are subject to approval by the board," he said.

In other investments, PTT opened its first service station in China with China's state refiner Sinopec in March, 1994, in the coastal city of Maoming. It plans to open 200 stations within five years in Guangzhou, Maoming, Shanghai, Tianjin and Dalian. PTT's budget would be 350 million baht ($14 million).

PTT, in a joint venture with Vietnamese state oil firms, will set up and operate a network of 50 service stations in Vietnam by 1999, it said last year. It plans to set up oil depots and LPG distribution and trading operations in Vietnam.

As part of its globalization efforts, PTT is contemplating expanding its oil-trading division in Singapore, where it at present has just a representative office.

"It's in the plan to make the Singapore office a more active center . . . PTT has made some investments outside Thailand. It wants to use Singapore to operate these if and when these are finalized," Mr. Wasantapruek said.