In articles on May 18, 1982, and on Jan. 16, 1983, The Post mentioned Ngo Vinh Long, a Vietnamese historian living in Boston. The Post did not mean to suggest that Long is in any way a representative of the present government of Vietnam or that he is that government's spokesman for policies or viewpoints.

Groups of Vietnamese refugees in the United States, prodded by nationalism, news from home and wishful thinking, are organizing and training in hopes of eventually overthrowing the communist government of Vietnam.

In "little Saigons" around this country, where 400,000 refugees are estimated to have settled after the war's end in 1975, dozens of competing groups have sprung up to raise money and support for the cause. Although their goals and origins differ widely, most say the Hanoi regime is rotting away, that its Soviet support is waning and that widespread passive resistance and sabotage in the country make a general uprising inevitable.

Some Vietnamese who disagree with the campaign or refuse to contribute money have been threatened and branded as communist spies in an ethnic community where that means ostracism. At least two deaths are believed linked to the factional disputes.

Otherwise, it is largely a war of words.

"The communist war machine is like a big tree," said activist Le Thi Anh of Cheverly in the poetic terms that nationalistic Vietnamese literature often favors.

"It has its roots in Vietnam but branches in Laos and Cambodia," where Vietnam-controlled governments are in power, she said. "The resistance is like a worm eating at the roots of the tree, and the resistance in Laos and Cambodia is like insects eating at the leaves."

The Vietnamese activists say they do not want U.S. help, at least not yet.

"One time already we tried that, and it didn't work," said Ngo Vuong Toait, publisher of a Vietnamese-language magazine and newspaper in Arlington. "We must show first we can do something ourselves, and then we can ask for help."

But critics, including some Vietnamese, say that the effort may be receiving at least quiet U.S. encouragement and that U.S. small arms may be flowing through China to Cambodian-based rebels, with whom the Vietnamese claim to have links. Refugee leaders also claim to be sending commando groups from the United States to harass Vietnamese authorities in Cambodia and Laos and to make guerrilla strikes in Vietnam.

Leaders of Vietnamese refugee factions tend to reply enigmatically when questioned about U.S. involvement and their sources of funding. "Indochina is not a high priority for President Reagan now," former South Vietnamese vice president Nguyen Cao Ky told a Tokyo audience last month. "But I assure you that they listen to our cause with a very friendly reception."

Ky, who runs a liquor business in Huntington Beach, Calif., said refugees were training in U.S. national parks for armed struggle. Internal resistance is so high in Vietnam, he said, that no foreign troop assistance will be needed.

"With 75 to 80 percent of the people against the regime, we don't need you," he said. "Give me guns, and we'll kick them out."

But the U.S. leader of another major faction, former Vietnamese army colonel Pham Van Lieu, denied that any military training was taking place on U.S. land and said Ky "does not represent anybody."

"We have no concrete aid but very good moral support from our American friends," he said smiling, and adding that money comes only from $6 annual membership dues in his group and from "private contributions."

State Department Vietnam specialists deny U.S. involvement in or encouragement for the refugee efforts, adding that centuries of cultural conflict also make it unlikely that the refugees have real alliances in Cambodia or Laos. They said resistance movements here and in Vietnam have more than nuisance value but should not yet be causing many furrowed brows in Hanoi.

Some critics go further. "The whole thing is a hoax. It serves other purposes," said Ngo Vinh Long, a Vietnamese historian living in Boston who frequently presents the Hanoi viewpoint in debates.

The real agenda, he said, "is to get money from the refugees and to intimidate them" so the U.S. government can "point to their sad stories and say next time the U.S. people should not intervene" in the conduct of a war.

Long, 37, twice suffered attempted firebomb attacks during speaking appearances last year and was roughed up in an elevator by Vietnamese who called him a communist butcher. A prominent antiwar student at Harvard in the mid-1960s, Long has maintained contacts in Vietnam. He traveled there in 1980.

The resistance, he said, "allows narrow-minded people in Vietnam with a bunker mentality to rationalize their policies . . . . The effect is to push things further and further toward a more undemocratic direction."

He agreed that economic conditions in Vietnam are disastrous but denied resistance leaders' claims that the government has lost all public support.

But Lieu and other nationalists say that relatives and friends in Vietnam write continually of guerrilla attacks and that sabotage efforts and work slowdowns in factories and farms are widespread.

"They're very isolated," he said of the government. "They care only for Russia, and Russia has too many problems to continue to pour $3 million to $6 million in there every day."

Troop morale is low and desertion rates are high, he said, claiming he saw 400 Vietnamese deserters who had fled to Cambodia when he was there last April.

"I think we will defeat them in three to five years, surely before the end of this decade," he said. The defeat will come not by invasion but by "a mass uprising of the Vietnamese people" encouraged by outside support from groups like his, Lieu said. "We already have plenty of guns."

Vietnamese-language publications, which have proliferated here, spread such views to those eager to hear them. Contrary reports from outsiders who say internal dissent is muffled in Vietnam cut no ice with the refugees. There are at least two dozen shoestring publications, most throbbing with patriotic poetry, songs, impassioned calls to action and vows to regain the homeland.

A recent issue of Viet Bao (Viet Struggle), the biweekly magazine published by Toait in Arlington, features emotional remembrances of Saigon, which is never called by its new name of Ho Chi Minh City; an essay exhorting refugees to self-examination, and a song titled, "Come to Vietnam and I'll Show You Why I'm Sad." One fictionalized account of prisoners' life in a "reeducation camp" is "like a document from Alexander Solzhenitsyn," Toait said.

In 1977, 102 former senior South Vietnamese military officers formed the Overseas Vietnamese Soldiers' Force in California, the first and still the most respected, if not the largest, U.S.-based resistance group.

According to its semimonthly journal Co Vang (Golden Flag), the group is dedicated "through violent revolution coordinated with political and diplomatic campaigns to destroy and wipe out the present regime of the brutal Vietnamese communists."

But action has not matched that rhetoric, according to Lieu, whose National United Front for the Liberation of Vietnam is the largest splinter group, claiming 50 chapters here and abroad.

"The generals had a chance to defend the country and they did not," he said. "Some people in the Soldiers' Force stop halfway to the goal."

The Soldiers' Force expelled Lieu, the National United Front chairman, former admiral Hoang Co Minh, and four others from its ranks in late 1981, calling them traitors seeking only publicity and personal wealth.

Hoang has subsequently been the most visible resistance leader. He met with Japanese politicians last year and makes speeches often cited by Lieu at organizing rallies.

Such gatherings took place last year here, in San Jose and Anaheim, Calif., Houston, Denver, Dallas, Portland, Ore., Rome, Marseilles and in cities in West Germany and Denmark, according to Hoang's backers.

One of them, Nguyen X. of Arlington, who asked not to be further identified, said each rally drew 2,000 to 5,000 Vietnamese, most wearing the brown shirts and tan pants of the group, to cheer the yellow flag with three red stripes of the nationalists.

He said "overseas" followers call themselves the Committee of Support for the Resistance Movement in Vietnam and have 100,000 members worldwide.

The rallies often feature a film showing Hoang and camouflage-clad soldiers toting guns and supplies through a jungle. Nguyen said Hoang went into Vietnam in August, 1981, with 200 guerrillas from the United Front, raiding Vietnamese territory and working with the underground there. Excerpts from the movie were shown by CBS News last March.

The underground includes the Hoa Hao, a reform Buddhist anticommunist sect in the Mekong Delta; another ethnic Buddhist resistance group called Cao Dy and a Montagnard group whose acronym is FULRO.

Refugee groups also claim to be "negotiating with" the fragile three-way opposition alliance in Cambodia that includes former Prince Norodom Sihanouk and his tiny Moulinaka group, the remnants of Pol Pot's communist Khmer Rouge, and former Prime Minister Son Sann's Khmer People's National Liberation Front.

Various analysts agree that any pact between the Cambodians and the Vietnamese refugees would be shaky indeed if it exists at all and would be based wholly on Sihanouk's need for military strength to boost his clout with the Khmer Rouge.

"So? They use us, we use them," Nguyen X. said, shrugging.

Any mention of help from China, which most recently invaded Vietnam in 1979, makes all of the refugee groups nervous.

"We don't want to talk about that at this time," Lieu said. China ruled Vietnam for 1,000 years, and, for many refugees, aid from that source would merely replace one communist ruler with another.

Still, representatives of several competing groups asserted that more than 20,000 Vietnamese refugees of Chinese descent are receiving military training in the southern Chinese provinces of Yunan and Kwangsi. "It's true they are there, but they are not our people," Nguyen X. said.

The refugee effort is not military but political, he continued.

"They really are armed propaganda teams, not meant to do any real damage but more for political mileage and repercussions," Nguyen X. said of the troops in Vietnam. "They engage in fighting when they are caught."

Hoang's critics, however, wonder if he ever made it over the Thai border, noting news reports there that he was arrested in Bangkok for a traffic offense about the time he was supposed to have been in Vietnam.

California publisher Dinh Thach Bich, one of the critics, said an FBI official had called to ask him about Hoang's fund-raising tactics. The FBI would not comment.

Ben Lee, an officer with the Los Angeles Police Department's Asian Task Force, said in an interview that while some Vietnamese gangs indulge in "outright extortion" with no political overtones, the front's tactics are more subtle.

"What they do is character asassination within the [Vietnamese] community," saying that those who decline to contribute are sympathizing with the communists, Lee said. "It leads to them being outcasts."

Two Vietnamese publishers critical of the refugee drive have been killed, although police said that both men had made many enemies and that their murders may not have been linked to this issue.

Lam Truong Guong, 25, who published California's only pro-Hanoi newspaper, was fatally shot in July, 1981, in San Francisco, and the previously unknown Anticommunist Viet Organization claimed responsibility. Last August, Nguyen Dam Phong, editor of a Houston newspaper called Tu Do (Freedom), was shot at his home. Neither case has been solved.

Le Thi Anh, 55, a longtime Vietnamese community activist, said the endless bickering among refugee groups must stop if the present regime in Vietnam is to fall. She was one of three persons selected for a coordinating secretariat at a kind of summit meeting that brought 78 group leaders here last Dec. 4-6 at the invitation of former representative Don Bailey (D-Pa.)

Bailey, who served in Vietnam, urged them to "set common goals and enumerate common principles" toward overthrowing Hanoi, but those have yet to emerge.

"The divisions are around leaders or ideas, whether focus on helping the boat people or on helping the resistance, also along religious or geographical lines," Le Thi Anh said. "Every Vietnamese wears a label . . . . Nobody dares to call a meeting because the other groups won't come."

Among the largest organizations attending were the original officers' group, the Vietnamese Soldiers' Force; the Democratic Coalition, based in Boston; the Hoa Hao from Vietnam, and the Overseas Forces for the Liberation of Vietnam, whose leader, Vo Dai Ton, was arrested in 1981 in Vietnam. He is widely regarded as a patriotic hero.

Hoang's group was the largest of several that did not attend. "The communists are always trying to paint us as U.S. puppets, and that is partly why we did not go," said Nguyen X.

But Le Thi Anh is working toward another gathering in April at which the factions will try once more to choose leaders and agree on action. She said "a Southeast Asian government" had agreed to help finance a radio station that would broadcast propaganda into Vietnam and that many other joint efforts were possible.

"We have no shadow coalition government here as they do in Laos and Cambodia," she said, "and we cannot form one just as a party of groups. We must see the liberation of Vietnam in the context of the liberation of those countries. None of us can do it alone.''