Doan Ngoc An is a boss' dream. The 35-year-old Vietnamese refugee is known as a tireless worker at the Beltsville electroplating plant where he works the 4 p.m. to midnight shift. He goes home, sleeps for three hours, and then gets up at 6 a.m. for his second job, delivering newspapers.

An, who arrived in this country in 1980, seems to be the epitome of industriousness that Americans point to in their praise of Vietnamese refugees.

But An's story is more complex. He says he is lonely, dreams continually about his family in Vietnam, and can think of little except returning to Vietnam to fight the Communists. He spends all his spare time making scrapbooks of Vietnamese history, scribbling anticommunist slogans in tiny writing across the faces of Ho Chi Minh and others.

"I'm not interested in making money," An said through an interpreter. "All I want is to go back. I want to liberate my country from the Communists . . . . It is not my ambition to be a millionaire or head of a business here."

This is not the usual Horatio Alger talk Americans expect to hear from newcomers to this country. But the 468,000 Vietnamese who have come to the United States are not typical immigrants. Vietnam was the first war this country lost, and out of obligation to those Indochinese who worked with the American war effort the United States made extraordinary efforts to resettle them here. The Vietnamese are among the war's few visible legacies in this country.

In the decade since their country fell to the Communists, many Vietnamese refugees have achieved extraordinary success in their new homeland, founding businesses, aggressively pursuing educations and happily embracing a new culture. Yet many others feel disoriented about their lives here and never cease mourning for the land they left.

"After 10 years, it's a bewildered feeling," said Mai Cong, an Orange County, Calif., mental health worker and Vietnamese activist. "It has disrupted us completely." The public ceremonies scheduled later this month at an Orange County college to express Vietnamese thanks to local and state officials, she said, will be "very, very difficult" for many Vietnamese, and she expects tears.

"It's 10 years of being separated from loved ones," Cong said. "It's mixed feelings, but it's not a feeling of joy. Even though many of us are successful and make a lot of money, we cannot help thinking what we've lost."

All first-generation immigrants, including the Europeans who packed American cities earlier this century, experience some disorientation and melancholy, according to social scientists. But specialists add that Vietnamese -- and the 263,000 Laotians and Cambodians whose countries fell to the Communists in the same year -- generally have experienced a more severe alienation than the other immigrants because they did not come to this country by choice.

Unlike previous immigrant groups, Vietnamese and other Indochinese refugees have received massive amounts of assistance from the federal government -- worth about $1 billion annually in recent years -- to ease their resettlement.

"I don't know of another situation in history where a nation has taken in such a large number of people from a distant culture for whom it felt a dramatic responsibility," said Roger Winter, director of the Washington-based U.S. Committee for Refugees. "We're investing financially and emotionally in these refugees, and incorporating them into our society so that, in effect, they become 'us.' "

Not surprisingly, it is the sons and daughters of refugees who are assimilating most easily.

"Nothing can stop me if I have the ambition," said Chi Luu, 26. "If you're good at what you're doing, you have limitless opportunities here."

Luu escaped from Vietnam by boat and made it to New York City in 1979, knowing no English. He worked for $3 an hour in a Chinatown grocery, then entered City College. He graduated as valedictorian in 1984 with a 3.98 grade point average, and now is a graduate student in electrical engineering at MIT. "My attitude here is to constantly learn," he said. Signs of Prosperity

But it's not just the young who have prospered. The signs of Vietnamese material success are evident everywhere they have settled in large numbers -- from Houston's South Belt neighborhood and the east side of San Jose to Arlington's Clarendon section, New Orleans and other cities.

In Orange County -- the center of this nation's Vietnamese culture -- Vietnamese own 700 businesses with annual sales of $300 million. About 85,000 Vietnamese live in the suburban county, a white conservative stronghold and surfing spot. Most of the businesses are in low-rise shopping centers along a mile-long stretch of Bolsa Avenue in the town of Westminster.

"We think the best way to be accepted by the American people is to become economically self-sufficient," said Luu Kiem Tran, a banker and head of Orange County's Vietnamese Chamber of Commerce. "We believe in the free enterprise system in America."

Westminster's shopping area had vacant storefronts before the Vietnamese came. Now Bolsa Avenue -- the largest Vietnamese commercial area outside Ho Chi Minh City -- is filled with restaurants, groceries and fabric stores. Everywhere, blaring from tape cassette players, one hears the sad, pitiful love songs of the Vietnamese about beautiful young women waiting at home for their loving men, all gone to war.

No matter how successful the Vietnamese are here, many are still haunted by memories of almost unimaginable deprivation or violence. The stories told by the "boat people" are especially gruesome. More than a half-million Vietnamese risked their lives by escaping on boats, and tens of thousands, perhaps hundreds of thousands, drowned or died of thirst or hunger, or were kidnaped or killed by pirates.

Doan Ngoc An was an MP in the South Vietnamese Army before April 1975, when he was imprisoned in a "reeducation camp." He saw many friends executed and starved to death by Communist guards before he escaped in late 1977, and later bribed his way aboard a leaky boat out of Vietnam. Thai pirates continually robbed them, raped the women and killed the men. He prayed to Buddha many times before reaching the United States in August 1980.

The Vietnamese who came in 1975 generally had the easiest time adjusting. Many were officials of the old regime, were educated and spoke English or French. They got jobs quickly, and studies show that by 1979 they more than doubled their earnings.

The second wave of immigrants, starting in 1979, included peasants and fishermen with less education. They have not adjusted as easily. A much larger percentage of them than in the first group have gone on welfare, and a number of their children have had problems in school.

"It's alienating and exhausting for some of these students," said Shirley Morrow, who works with Indochinese students at Arlington's Wakefield High School. "They're doing things they should have done when they were six years old."

Having lived much of their lives in the countryside, many of these Vietnamese are stunned when they enter supermarkets or shopping malls. Others have chopped chickens on kitchen floors or cooked meals in living rooms over open fires before social workers advised them otherwise.

The psychological burden is immense. The disintegration of their families, for centuries the foundation of their culture, can have a devastating impact. "They become aware of their dislocation; they feel grief, and they have a great sense of inadequacy," said Kim Cook, a Vietnamese mental health counselor in Arlington.

A 1982 consultant's study for the Social Security Administration, consisting of interviews with 555 Vietnamese refugees, found that 65 percent said "the overall quality of their lives" is lower here. The consultant described the problem as "a sense of deterioration" in family life.

A Vietnamese doctor in Orange County is a case in point. The doctor, who declines to be identified, recalls that during his family's 1975 escape by boat his 11-year-old daughter was swept overboard. Now he and his wife are confronting a ne difficulty more familiar to Americans: His 19-year-old daughter has left the family to join the Hare Krishnas. "Ten years later, we have no answer for this, either. Why did she leave us?"

Some parents are so concerned their children are becoming too Americanized that they are sending them to special classes to learn their native language and national traditions.

"For so many Vietnamese, both husband and wife work, and they don't have time to teach the children traditions," said My Hien, an Arlington social worker who helped organize one such summer school that instructs 500 Vietnamese students. "We say to the children, 'Be proud of your roots.' "

But some Vietnamese youngsters reject their heritage. "Randy" Tuan Ly, who left Vietnam with his parents in 1975, said he never learned the rudiments of Vietnamese culture because his parents were too busy working here to teach him. Ly, now a senior at J.E.B. Stuart High School in Fairfax County, moved out of his parents' house last year after arguing bitterly with his father over his job as a lifeguard and his playing on the school's varsity football team -- activities the father thought were un-Vietnamese.

Ly decided he hated being Vietnamese, "permed" his hair, changed his name to "Leigh" and ignored other Vietnamese students. But after Vietnamese teachers taught him more about his heritage, he assumed his Vietnamese name again and took a new interest in Vietnamese culture. "For the first time I learned about Vietnamese history, family life," he said. "I didn't know who I was. Now I'm proud of being Vietnamese. I realized, 'What would my grandfather say about me changing my name?' "

Vietnamese point to other signs of the breakdown of their families. One is the presence in many Vietnamese communities of young street gang members -- most of them unattached men with no families in this country -- who get into fights, practice extortion and commit robberies and other crimes.

"We're not afraid of the Americans, the blacks, the Hispanics," said one Vietnamese jeweler in Orange County. "We're afraid of the Vietnamese. They know our language. They take our money, we're ruined. It's what gives me these gray hairs."

"We're talking about people who've lived with violence," said Capt. Donald Saviers, the Westminster police department's Vietnamese specialist. "A lot of the violent acts aren't reported because the people just accept it as part of their lives."

Saviers said that although the Vietnamese make up only 18 percent of the California town's population, they account for 40 percent of the arrests. Many Vietnamese distrust police and do not report crimes, Saviers said. Reliance on Welfare

While the newcomers are concerned by crime in their community, social workers and government officials are puzzled by another aspect of their adjustment here: their reliance on welfare. The concern is greatest in California, where 85 percent of the state's eligible Indochinese refugees are on public assistance, compared with 18 percent in Texas.

The difference in the welfare rates can be traced in part to California's higher payments -- $625 a month for an adult and three children under one program, compared to Texas' $178. In addition Texas agencies are more demanding in requiring refugees to find work. California's higher payments -- along with its warm weather -- also have attracted tens of thousands of Indochinese refugees from other states.

Some officials believe the high welfare rate contradicts the Vietnamese's reputation for hard work.

"The attitude is, 'You owe us. You lost our war,' " said Phillip Hawkes, director of the federal Office of Refugee Resettlement. Hawkes and other federal officials say some state welfare systems, including California's, encourage Vietnamese to go on welfare and learn English before prompting them to get a job. California officials deny the charge.

"I don't care how strong your work ethic," said Rep. Daniel Lungren (R-Calif.), who represents many Vietnamese and other Indochinese, "you're going to have trouble resisting welfare" under those terms. "How do you wean people away from a welfare system that's been their umbilical cord to society?"

Vietnamese leaders deny that their community misuses welfare and say time on welfare is used to learn English and a trade before getting a good job.

"They feel if you take the first job as a cleaning man, you learn nothing, and you'll be a cleaning man for life," Cook said. "Any refugee who's not stupid is going to take advantage of it. It's like a tax break."

Faced with the high costs of resettlement, some state and federal officials recently have shown signs of what Sen. Alan K. Simpson (R-Wyo.) calls "compassion fatigue" for the newcomers, refugee activists said.

Policy makers warn that unless the costs go down, there will be a backlash, and the doors will be closed permanently to the several hundred thousand Laotians, Cambodians and Vietnamese in refugee camps in Asia waiting to come here.

"The problem is the patience of the American people is not unlimited," Lungren said. "Some are responding, 'Why should refugees get a leg up on me? My taxes are going up" for them.

Meanwhile, 1,500 Vietnamese are leaving Vietnam by boat each month. Another half-million have asked the Communists to let them leave. The U.S. government is welcoming up to 50,000 Indochinese into the country this year -- a drop from a high of 166,000 in 1980.

"Our position ought not to be, 'It's been 10 years now, let's stop,' " said Winter, who served as president Jimmy Carter's refugee chief. "It ought to be, 'What are their needs? What are our obligations? . . . . We should feel a continuing obligation."

The Vietnamese refugee program is so vulnerable, government officials agree, in part because refugees have almost no political leadership or organization. Guilty About Freedom

Many Vietnamese are still preoccupied with life in their homeland. Most refugees send money and goods to impoverished relatives there, and anxiously wait for word back. "They feel guilty they have freedom and security, and there are so many relying on them back home," said Yen Do, editor of a Vietnamese newspaper in Orange County. "They can never get away from their oppressors. It will follow them for their whole lives."

Reluctance to break those ties is thought to be a reason why only 16 percent of the Indochinese refugees who are eligible have become citizens. And Vietnamese say that political involvement is discouraged by an atmosphere of distrust found at all levels of their society here.

The Vietnamese communities are severely split by factions with, for example, former Army officers criticizing their counterparts from the Navy, reformers against the old line, class against class, and on and on. The exile press is filled with accusations that one or another leader is a "Hanoi henchman," a "puppet" of corrupt South Vietnamese generals, a CIA agent or a sellout to the Americans.

Vietnamese widely believe that Communists have infiltrated the refugees here. Many claim that details of secret meetings of anti-Hanoi groups have appeared in radio broadcasts in Vietnam. Federal law enforcement officials say they also believe the Vietnamese communities are shot through with spies.

"We come from a war-torn society," said Yen. "It's in the nature of things, the secrets, the divisions."

This atmosphere of intrigue surrounds the activities of the shadowy but apparently active resistance movement that aims to overthrow the Hanoi government. There are more than 50 such competing organizations here, and many issue harsh condemnations of one another.

Despite the infighting, almost all Vietnamese here support the aims of the resistance. It is almost a rite of adolescence for many male Vietnamese teen-agers to talk about returning to Vietnam to fight the Communists.

Yet Vietnamese youths also acknowledge their futures are not in Vietnam, but in the United States. Their parents know that their children, for better or worse, have been caught up in the American dream.

"I'm on the track team, I run the 880 relay, the mile relay and the 85-meter dash," said Thu-Nga Hoang, a lithe 16-year-old girl who is a straight-A sophomore at J.E.B. Stuart High School. "I play in the orchestra, first chair, second violin; I'm in the French club, the science club, the international club."

Thu-Nga cannot remember the name of the town in Vietnam that she left at age 6 with her family, and has forgotten Vietnamese, but she's confident about her life here. "I really think I'm going to be able to do whatever I set out to do," she said. "I think it's going to be strict studying until I reach my goal."