Apparently intensifying efforts to assimilate its southern half, Vietnam has launched a campaign to stamp out Western cultural influence here and bring this city's bustling black markets under control.

The measures, which one foreign resident likened to a small-scale Cultural Revolution, appear to be part of a general tightening politically in order to consolidate communism in southern Vietnam.

As such, the measures seem likely to deepen the general despondency that is so evident everywhere in this former South Vietnamese capital, which was renamed after the 1975 communist takeover but which most residents still call Saigon. The dissatisfaction with Hanoi's rule extends even to longtime Communists and sympathizers who supported the struggle to unify North and South.

The bloodbath that officials in successive American administrations predicted if the South fell did not occur here. The harshest features of communist rule in the North have not been imposed on the South, where people still feel relatively free to speak their minds in private.

But in the last several weeks, the authorities have seized literature from the city's popular used-book market, closed many small private cafes, confiscated imported music cassettes and prohibited foreign currency holdings by Vietnamese.

"It's a sort of Cultural Revolution to pull Saigon away from foreign influences," said a well-informed foreign resident. "This is the first time it has been done so systematically."

"The government is turning the screw," said another. The campaign, he said, demonstrates that "six years after the revolution, the South still hasn't been assimilated."

According to government spokesman Nguyen Phuong Nam, these actions do not amount to "a campaign against Western culture, just against decadence."

Nevertheless, such measures are seen here as part of Hanoi's relentless effort to build a socialist society regardless of the political and economic cost of increasing the South's alienation.

Some of this alienation seems to be shared even by longtime Communists in the South who support Hanoi's aims but disagree with its methods.

"We shouldn't say everything that comes from Europe is bad, or say it is a model either," said Duong Quynh Hoa, a former health minister in South Vietnam's Provisional Revolutionary Government, which was the political arm of the Vietcong. "This is not an example of democracy."

Hoa, currently director of a pediatric hospital here, made her sharpest complaints about the economy, especially shortages of food that she said were slowly sapping the strength of the work force. She blamed the problems in large part on the government's "conformism and dogmatism."

"When we achieved the liberation, we thought things would be better," she said. Asked if she were disappointed, she sighed and said, "I am exasperated. We could have done better with all the resources we had. We didn't exploit the human factor, the cadres who were already here. We used those who weren't much good, and rejected those who were."

Although she ardently supports Hanoi's effort to "build a socialist society," Hoa acknowledged that "the population of Saigon still is not motivated to see the foundations of the government's economic measures." This she blamed in part on a "lack of initiative" by government cadres, who "wait for every order to come from above." The government's "conformism," she said, "remains a force of inertia."

Despite even greater dissatisfaction among noncommunist Southerners, "the population is largely passive," a foreign resident said. "The people are morose. They have lost hope. They don't believe in organizing an opposition. People prefer to leave the country."

Indeed, an increase in illegal departures seems to be one likely result of the measures. Already, it is difficult to meet any resident of this city who does not want to emigrate. Although people evidently are becoming more fearful about expressing them, complaints of a stifling political, economic and social atmosphere seem to pervade all strata of society.

This was the impression gained from conversations with about a dozen Vietnamese met at random during a week's stay in Ho Chi Minh City on a transit visa, which precluded any interviews with senior government officials or travel outside the city. While many Vietnamese seem reluctant to be seen talking to a foreigner in public, they express their feelings fairly frankly and readily in private, even though there may be some risks in doing so.

All this indicates that although Hanoi is clamping down, its control is not pervasive enough to suppress people's complaints.

"Everybody wants to leave," said a ragged pedicab driver. "Believe me, 99 percent of Saigonese don't like communism. We are under the fist of the Communists." He said he hoped to borrow enough money to finance an illegal departure by boat.

"The regime is becoming tougher," said a relatively well-off Vietnamese who publicly opposed the government of former president Nguyen Van Thieu, which collapsed shortly before the fall of Saigon on April 30, 1975. "We don't miss the old regime, but we miss the old days," said this source, who also seeks to leave.

The dissatisfaction extends to a Cambodian immigrant who fled his country's communist Khmer Rouge government, before it was overthrown in January 1979 by Vietnamese invasion troops. He said he did not want to go back to Cambodia, where his entire family was killed by the Khmer Rouge, because he was afraid of getting caught up in another war.

"I have to leave," he said. "I'm all alone here. I live from day to day. I don't have a job because there are no jobs here. And there is no freedom."

Wearing tattered jeans and a soiled cap, the 36-year-old Cambodian confided that he had already tried to leave illegally by boat three times beginning in 1978 and had been caught and jailed each time -- the first for six months. But he said he planned to try again, this time by going overland through Cambodia to the Thai border. He said he was aware of what might happen if he were caught by the Khmer Rouge.

"I realize the trip is dangerous, but I have to try my luck," he said. "It's better to die that way than to die slowly here."

Some of the general discontent seems to be taken out on the country's estimated 4,000 to 6,000 Soviet advisers, who are much in evidence here. Westerners taken for Soviets are frequently subjected to disparaging remarks. The biggest complaint seems to be that the Soviets do not spend enough money to suit the Vietnamese, who derisively call them "Americans without dollars."

"People don't like the Russians because they're poor," said a student. "Wherever the Russians go, they bring poverty."

Although the Soviets reportedly are pouring more than $2 billion worth of aid a year into Vietnam, "the economy is in complete decline," said a foreign observer. The country has been suffering from chronic food deficits, a lack of exports, high inflation and the unproductive effects of the continuing war in neighboring Cambodia, where Vietnamese troops are battling Khmer Rouge forces.

Rations of basic foods are meager, poor in quality and difficult to obtain at inexpensive state-run shops, and the same items are at least 10 times more expensive on the free market than they were before the communist takeover. In addition, private merchants are increasingly unhappy because they are being taxed more and more, residents said.

A measure of the economic decline was the devaluation last month of the Vietnamese currency, called the dong. From an official tourist rate of four to the dollar, the dong was suddenly dropped to nine to the dollar.

The rate for official business remains at about 2.7 dong to the dollar, but on the black market the U.S. currency fetches around 40 dong.

"The dong has lost its value as a pricing unit," said a foreign resident. Ironically, he said, "the pricing unit in Vietnam has become the U.S. dollar."

In an effort to gain control of the black market in dollars and help build the government's meager foreign exchange reserves, Vietnamese authorities are introducing a system in which foreign visitors will have to pay for everything in foreign currency -- preferably American -- under government control. According to the new rules being implemented this month, foreigners will be required to surrender their currency on arrival and be issued coupons in exchange at the official rate. On departure, they are supposed to cash in any unused coupons against their deposits.

"This proves that the Vietnamese economy is near its last gasp," a foreign resident said.

Another aspect of the new measures is that Vietnamese will no longer be allowed to hold any foreign currency. However, there is some skepticism about whether this measure can be enforced.

"We'll see if the government can apply the new regulations," one Vietnamese official said.

The other elements of the clampdown seem to be motivated by ideological rather than any economic considerations.

The campaign against Western books reportedly began two months ago with the confiscation of volumes of fairy tales, which authorities judged not to be "constructive" reading for children. Soon afterward, the authorities closed the city's renowned used-book market and, on the pretext of making an inventory, confiscated all books judged "reactionary," according to a foreign resident. These included mysteries, romantic novels and histories of the eras of French colonialism and American involvement in Vietnam.

On a recent visit, about half of the bookstalls were closed, and the rest were selling mostly Vietnamese books about communism or the 1975 victory. Virtually the only English- or French-language books on display were technical manuals, language instruction texts or dictionaries.

Even so, some banned books hidden during the confiscation can still be purchased under the counter. Among the tomes furtively offered to a browser recently was a copy of Victor Hugo's "Les Miserables."

The closure of the book market followed a crackdown on cafes, residents here said. Most disturbing to authorities, apparently, was the countercultural atmosphere of these hangouts, in which idle, disaffected youths would listen to cassettes of Western rock music and Vietnamese songs by singers living in exile abroad.