Old Saigon is dying. In its place is growing up a new city with a new name, a city that is already quieter, smaller, less cosmopolitan.

It is probably already better for many factory employees and other workers. It is worse at least economically, for much of the middle class and for many of the self-employed.

The city is already losing its American influence. There is no more Coca-Cola. The plant has been shut down, although a glass factory still turns out the familiar "Coke" bottles used for a local soft drink.

The motor traffic is much reduced, including the motorbikes, three-wheel Lambreta jitney buses and motorized pedicabs whose defective mufflers used to cover Saigon with a permanent blue haze.

Saigon's lavish French and Italian restaurants, with their huge menus and expensive wines, are mostly gone with the American's and the American dollar. One of the few still operating - at a limp - is the Pizzeria.

"Steve," the glib Vietnamese born Chinese who runs it, said he planned to close in five or six months and go to Hong Kong, where his family lives. He complained that taxes are too high that the new government is too friendly with Russia and that Larue beer, which sells for 1 dong (44 cents) for a large bottle in government-run hotels, costs him 5 dongs on the free market. He sells it for 7.

The street outside - once Rue Cantinat, then Tu Do Street and now Dong Khoi (Simultaneous Uprising) Street was almost deserted at 9:30 p.m. There was only one other party in the restaurant, a group of Swedes. A beggar peered at the diners through the grating over the front window.

The prostitutes who used to crowd the joint along Tu Do and drink tea "cocktails" with American Gls were gone, many to schools for "restoring the dignity of women." On a visit to one of the schools, hundreds of young women were seen learning to make baskets and doormats. A class was learning to read and write from a 24-year-old former prostitute who had an eleventh-grade education.

The young women are confined to the school for the six month initial course. An official said almost all had to be treated for venereal disease. Three hundred have "graduated" to take useful jobs, he said.

The swarm of beggars and pimps who used to line the walk next to the veranda of the old Continental Palace, once a hangout forWestern soldiers, spies and journalists, are all gone. Only a half-dozen beggars were seen on this visit, mostly in the central market.

Streets are not entirely safe even in the daytime. Visitors to the city, including Vietnamese from Hanoi, customarily remove their wristwatches before venturing into crowds. Small boys still can grab a watch in a flash from an unwary stranger.

Officials say there are still 15,000 to 2,000 drug addicts on the city's streets. Before Saigon fell there were said to be 150,000. Ninety per cent of the addicts were said to be on heroin during the war, switching to opium when the heroin supply was cut off at "liberation."

Saigon's wartime peak population of 4 million has already been cut to 3.3 million, mostly by the return of former peasants to the underpopulated countryside.

MANY OF the landmarks of old Saigon have changed. Independence Palace, where dessident Vietnamese airmen tried to bomb President Ngo Dinh Diem in the early 1960s and where Viet Cong troops besieged President Nguyen Van Thieu in 1968, now stands empty, said to be undergoing repairs. Across its front is Ho Chi Minh's omnipresent slogan. "Nothing Is More Precious Than Independence and Freedom."

The My Can floating restaurant still does a capacity business, although now with ordinary Vietnamese. The Viet Cong once attacked it, first with a bomb from the river and then with a Claymore mine blast that caught U.S. servicemen fleeing down the gangplank. It still charges 10 per cent for "service", a practice unknown in the North, where tipping is deemed a degrading capitalist device to depress wages.

Old Saigon's Cercel Sportif, where wealth and status were required for membership, has been turned into a sports club for workers, providing swimming, tennis, table tennis and volleyball at nominal rates. It appeared widely used and well run, although two groups where playing tennis on courts that lacked nets.

But for all the change, the city retains much of its old character. Crowds still eat their meals of rich noodle soup at tiny sidewalk tables and buy food, clothing and house hold supplies in the noisy, jampacked markets, where prices are uncontrolled and bargaining is expected.

Street merchants stillhawk sunglasses and spread out an array of stationery, Bic pens, shoes, plastic sandals, toilet articles, U.S. Army gear and clothing, embroidered blouses, padlocks, flashlights, hypodermic needles and surgical instruments.

Parks, coffe shops and motion picture theaters are crowded in the early evenings. People still flock to the beach at Vung Tau by bus or motorbike, and some disputed a Communist official's claim that only the rich could go there in the old days.

AT THE DUSTY Mckong Delta town of Tan An. 50 miles southwest of Ho Chi Minh City, 300 former junior officers of the South Vietnamese army are still inmates in a Communist "re-education camp" which held 900 when it opened in June, 1975.

The camp is a collection of dilapidated sheet metal bar racks at the edge of a weed-covered airstrip once used by an American artillery unit. Outdoor toilets had been dug nearby with no roofs to protect against the rain or sun, and only waist-high fencing of old sheet metal provided minimum privacy.

The camp is only lightly guarded. Without rations or identity cards, the inmates would be worse off if they ran away.

A dormitory inspected at random had 40 narrow wooden pallets 6 inches off the cement floor, touching each other side by side, with thin straw rolled up at the heads of the beds serving as mattresses. Above the two lines of beds were wires to hold mowquito netting. Malaria still is a problem wherever mosquitoes breed in unfilled bomb craters.

The camp visitors center was another barracks, its single big room furnished with grouped chairs and benches for monthly three-hour visits by the inmates familes.

GOVERNMENT OFFICIALS have been concerned about the bad name the camps have been getting abroad, including charges that they penal colonies for indefinite imprisonment of political enemies. In an effort to undo the damage, they are again permitting selected foreign news correspondents to visit the camps. A Hungarian reporter was said to be the only previous foreign newsman to have visited this one, just outside the capital of Long An Province.

Like all the other re-education camps, it is run by the army. The original roster has been gradually reduced. Officials said the are awaiting action on a recommendation to release another 100.

The camp's military commander accompanied this reporter on a three-hour tour, answering most questions and permitting random interviews with inmates. With the commander and Communist cadres from Hanoi looking on, the inmates could hardly have been expected to complain about the government or the way the camp was run, but their comments on their daily lives seemed beyond question.

Five who were interviewed all said their families had visited them within the past month, bringing gifts of fruit and cake. They sid they sent and received letters regularly, with only three or four days for delivery.

They confirmed the commander's statement that their monthly rice ration was 18 kilograms (almost 40 pounds), the usual ration for persons doing heavy manual work. All said they had had bread and tea of breakfast and rice and duck the previous noon and night. All of those questioned and observed were working industriously and appeared healthy and alert.

Camp officers said inmates were considered eligible for release when they had completed a course of study to explain the policies of the new government, to "improve their knowledge and understanding and relate them to the realities," and had learned a civilian trade.

The camp political commander said the inmates gradually reach an understanding that "the former regime was based on money and exploitation while the present regime stands for socialist construction."

When would the last inmates be released? The officer expressed surprise at the question and said the government's plan provided that no one would be kept in a camp longer than three years. He said that meant that this camp and all others would be emptied by May, 1978.

A provincial officer at Sa Dec, a Mekong Delta city southwest of here, had said that some fo the 160 persons remaining in camps in Dong Thap Province might be held longer than three years "for their own protection, because the people hate them for their crimes."

The commander here, informed of that statement, said exceptions would be made for special cases where the inmates had committed serious crimes during the war or proved to be resistant to the camp study program.

QUESTIONING in other parts of South Vietnam showed that many former military officers and civil servants now are free of any special restraint and at work alongside other citizens. Many of the civil servants have returned to their old jobs.

For enlisted soldiers and lower-level civil servants it was said there was only a perfunctory "re-education" of three days or in many cases none at all.

Efforts to interview specific individuals some of whom had been in re-education camps and whose treatment has become an issue among Vietnamese refugees and among members of the old U.S. antil-war movement, were largely unsuccessful.

Tran Ngoc Chau, who was imprisoned by the old regime because of contacts with a brother who had sided with the North, was not "available". A well-informed Vietnamese said Chau had been under house arrest until early October but now was free.

There was no official response to a request to see Tran Van Tuyen, a lawyer who was active in the opposition to the old regime. The same source said Tuyen was in a re-education camp.

Thich Tri Quang, a Buddhist monk who brought the government and the war to a halt for a time in Hue and Danang in 1966, was said to have received this reporter's request for an interview, but there was no response, whether by his won decision or through action by government.

The re-education program was obviously an emergency security measure in the early months after the Communist victory, when the new regime was consolidating its control of the South. It still has its security aspect as regards high-ranking civilian and military figures in the old regime and stubborn opponents of the new rule.

By putting members of the defeated opposition through a political purification process it also seems, in the view of several Western diplomats in Hanoi, to have headed off any possibility of the "bloodbath" that former President Johnson and other U.S. political leaders had been predicting for many years if the Communists won.

It seems a fair appraisal that the re-education program, grim adn uncomfortable as it is, is not at all the concentration camp system it has been pictured as being by some outside critics.