The Malaysian government assured the world tonight it would neither shoot Vietnamese refugees nor evict them from camps, but warned other countries it is losing patience with the slow pace of resettlement.

Attempting to clarify reports that had caused a worldwide alarm, Malaysian officials insisted there had been no drastic change in policy but emphasized they will continue to block landings by new refugees.

In a letter to U.N. Secretary General Kurt Waldheim, Prime Minister Datuk Hussein Onn declared: "I wish to state that our measures to prevent further inflow of the boat people do not include shooting them."

But he said that if the refugees are not eventually settled in third countries, Malaysia will either force those sheltered here back into the sea on boats or leave them "to rot" in their camps.

His statement contradicted the assertion last Friday by Deputy Prime Minister Datuk Mahathir Mohammed who, according to several news agencies, threatened that new refugees would be shot and that the estimated 75,000 in camps here would be put back to sea. He also was reported to have said that Malaysia is building a fleet of boats to faciliate the refugees' expulsion.

Over the weekend, government forces turned back 500 refugees attempting to land, carrying out a get tough policy adopted last February to prevent Malaysian camps from being swamped by a rising tide of drifting boat people.

The action reflected the hardening attitude of Southeast Asian countries toward the refugees who have been streaming out of Indochina in recent months. Indonesia ordered security forces to prevent entry to all incoming Vietnamese. Thailand has pushed thousands of fleeing Cambodians back across the border to face an uncertain fate. Malaysian Deputy Prime Minister Mahathir's declaration last Friday that new refugees would be shot on sight had seemed to be the most drastic of the latest plans to repel refugees.

The Malaysian government disclosed tonight it has turned away boats carrying an estimated 40,000 people already this year. Several of those boats are known to have sunk at sea.

"We have reached the limit or our endurance and this is the only way open to us to contain the problem that is severely affecting our country," declared Prime Minister Hussein.

Attempts to explain away the initial reports added to hte confusion tonight. Some observers thought the deputy prime minister had made the remarks in an offhand comment to reporters to satisfy domestic opinion, which is opposed to accepting refugees even temporarily, and to prod other nations to resettle refugees faster.

In a long, rambling news conference, Home Minister Tan Sri Ghazali Shafie at first said the deputy prime minister had merely threatened to "shoo" the new refugees away, not to "shoot" them.

But later Ghazali said the high official had been trying to explain to reporters that there was no legal authority to shoot refugees even if the government wanted them shot.

Ghazali also emphasized there are no plans to send the Vietnamese back to sea, although at one point he confirmed that the government has begun to build boats for that purpose.

Hussein Onn, the prime minister, stressed in his letter to Waldheim that Malaysia would not permit any of the refugees to remain here indefinitely.

"Therefore, if they are not accepted by resettlement countries or their country of origin, we will have no choice but to send them out, which is the only alternative to their being left to rot in the camps."

That has long been Malaysian policy and there seems to be no imminent threat of eviction. Ghazali said his government would continue to await new resettlement plans from such countries as the United States, England, France and Australia before resorting to eviction.

"We will decide on this when we decide that all the promises from third countries are just promises, promises, promises, in other words until it is clear that this [resettlement] is not going to be done."

Malaysia is the first goal of most of the Vietnamese refugees who have left home in the past four years in what now is assumed to a deliberate Vietnamese government policy of expelling dissidents, particularly those of Chinese descent.

Since 1975, according to Malaysian statistics, 117,778 refugees have landed here after crossing the South China Sea and 42,248 of them have been resettled in other countries, about half in the United States. That has left 75,530 lodged in three crowded camps on Malaysia's east coast. More than 40,000 of them are in a camp on the island of Bidong, less than one square mile in size.

Thousands of others have died at sea while others have drifted on to Indonesian waters or made it to Hong Kong.

A new outpouring of refugees this spring has caused Malaysia to toughen a long-standing policy of attempting to force arriving boats back out to sea with supplies of food and water.

Since January, Ghazali said tonight, the government has towed away 267 boats loaded with more than 40,000 people.

He stressed that the tow-away policy would be further strenghtened this month when more navy ships move to the east coast. The government already has established more than 100 coastal observation points to spot incoming boats and has committed about 2,000 army troops and police to the tow-away policy.

While blaming Vietnam as the source of the problem, Ghazali noted that that country has offered to begin talks to achieve an orderly emigration of refugees.

"We must seize this opportunity," he said, suggesting that the United Nations establish evacuation camps for willing emigrants on Vietnamese soil.

Third countries must hasten their resettlement programs to accommodate those thousands certain to come out of Vietnam in the near future, he said.

Reaction to the refugees' plight also came from other world capitals. In Paris, French President Valery Giscard d'Estaing joined British Prime Minister Margaret Thatcher in calling for an international conference to deal with the situation. Foreign ministers of the European Common Market countries, meeting in the French capital, joined the appeal.

In London, Foreign Secretary Lord Carrington announced plans to visit Hong Kong and Malaysia after the Tokyo economic summit scheduled for later this month.

Washington Post correspondent Jay Mathews reported from Hong Kong that officials of the tiny British colony are worried that Malaysian threats to expel refugees may force more "boat people" to attempt the hazardous and much longer ocean voyage to Hong Kong.

Officials in Hong Kong say they expect some reduction in the number of refugees when the monsoon rains begin, but "the number is still far higher than we can expect," according to one spokesman. CAPTION: Picture, Nationalist demonstrators in Bangkok, Thailand, gather in front of Government House to demand the expulsion of all Indochinese refugees. UPI