In an effort to capitalize on recent Thai military strikes against the Golden Triangle's leading opium warlord, the Burmese Army has sent three troop battalions to attack the drug kingpin's rebel force in the rugged mountains of eastern Burma, according to diplomats and Burmese sources.

The Burmese operation threatens to disrupt further the opium and heroin trafficking activities of the Shan United Army, a Burmese rebel group led by Chang Chi-fu, who is regarded by the U.S. Drug Enforcement Administration as the world's biggest narcotics dealer.

However, the splintering of the group of rebel Shan tribesmen, some foreign and Burmese sources fear, could also contribute to the growing involvement in the drug trade of the Burmese Communist Party, which is supported by China and is the biggest armed group battling the Burmese government.

The Thai attack on a Shan United Army stronghold in a Thai village deeply gratified Burmese authorities, who had been soured by years of Thai inaction, the sources said.

Now the two sides are showing signs of dropping their longstanding mutual suspicions and moving toward some coordinated military action against the drug trafficking "armies" that also ostensibly seek independence from Burma for their tribesmen. The fertile Golden Triangle drug-growing area also includes some Laotian territory.

Thailand is preparing to send a high-level team of narcotics officials to Rangoon early next month to confer with their Burmese counterparts and "try to coordinate some sort of action," a well-informed Western official said. The United States has long encouraged this sort of cooperation, but the Burmese in the past have suspected corrupt Thai officials of leaking word about impending antinarcotics operations to the traffickers.

According to a U.S. narcotics official in Bangkok, the Thai strike against the Shan United Army last month was "pretty successful, but if there had been coordination with the Burmese it could have been twice as successful." As it happened, sources here said, there was no joint planning, and the Thai action came as something of a surprise in Rangoon.

In the raid, Thai Border Patrol Police backed by Army troops, helicopter gunships and U.S.-supplied OV10 counterinsurgency planes captured Chang Chi-fu's stronghold in the Thai village of Ban Hin Taek, forcing him and his heavily armed followers to take refuge across the Burmese border.

Besides prodding the Thais and Burmese toward cooperation, U.S. authorities are preparing a new increased antinarcotics aid program for 1982. The level of the aid is to be raised to $5.8 million this year from $4.6 million in 1981, officials in Bangkok said. Most of the money is earmarked for support and maintenance of 26 Bell Huey helicopters and several Fokker transport planes supplied by Washington under a 1974 agreement.

Other elements of the aid package are a classified communications assistance program and help in the government's efforts to make rural farmers substitute other crops for their opium poppies, officials said.

The supply of the helicopters, which were unarmed and meant to be used for transport, has drawn protests from tribal groups that claim the U.S. equipment is being used to suppress their quest for independence.

In 1976, one group, the Karen National Union, wrote to the White House complaining that the helicopters were being used against all Burmese insurgent groups, not just in antinarcotics operations. Washington apparently dismissed the claim. About 20 rebel groups oppose the Burmese government.

According to one Western diplomat here, "All insurgent groups active in Burma are involved in some way in narcotics." Even members of the Karen National Union, one of the least involved groups, have been reported to guard opium caravans traversing their territory along the border with Thailand, the diplomat said.

Some of the helicopters were used last year in Burmese military attacks that knocked out at least three heroin refineries near the Thai border, Burmese sources said. The helicopters have also been used in attacks on opium caravans and supply routes, diplomats said.

In the latest Burmese operation, which began at the end of last month, three battalions were sent to intercept Chang Chi-fu's forces in the border area across from Ban Hin Taek, with other Burmese troops deployed in the vicinity as potential reinforcements, officials said. So far as is known, however, only one minor clash has resulted, leaving one Burmese soldier and two Shan United Army troops killed.

Chang Chi-fu and some of his estimated 3,500 troops reportedly are near the village of Mong Young in Burma, close to an area controlled by the Burmese Communist Party. Following the attack on his Thai headquarters, Chang Chi-fu threatened to join forces with the Burmese Communists, a statement regarded as a negotiating ploy.

Most of the opium produced in Burma, which accounted for about 75 percent of the Golden Triangle's 600 metric-ton harvest last year, comes from poppy fields in areas under the sway of the Burmese Communists. Until a few years ago, the party allowed groups such as the Shan United Army to buy opium from its area's villagers. But then the Chinese suspended financial assistance to the party in an effort to improve relations with the Rangoon government, and the Burmese Communists became major opium traffickers, according to diplomatic and Burmese sources.

Although cash has been cut off, China still supports the Burmese Communist Party with arms deliveries, training and medical supplies, the sources said.

Since last year, the party also has become involved in refining opium into heroin and runs two refineries, a well-informed Western official said.

"Next to Chang Chi-fu, the Burmese Communist Party is the biggest opium trafficker" in the Golden Triangle, said a knowledgeable Burmese source.

Now the main question is whether the party will use its estimated 20,000 troops to try to take advantage of the Shan United Army's current disarray, diplomats said. So far the Burmese Communists have not appeared to react, but observers here are watching for signs that the party may move to seize a bigger share of the narcotics business.