In an urgent effort to buy time, Secretary of State Cyrus R. Vance asked leaders of five Southeast Asian nations today to reverse their stand and accept Indochinese refugees temporarily until they can be resettled elsewhere.

He told foreign minister of five countries that a "major international effort" is under way to help and asked them to reconsider their jointly stated refusal to accept any more refugees.

Vance also said that their agreement to grant asylum to refugees streaming out of Indochina could help the Carter administration win congressional support for extra money to care for the refugees.

The immediate reaction from the foreign ministers was cautious.

"What we heard from Secretary Vance I will report back to my country," said Malaysian Foreign Minister Tengku Ahmad Rithauddeen, whose government continues to push hundredsof refugees back to sea each week.

Today the Malaysians intercepted three boats loaded with more than a thousand refugees and towed them back out to sea.

Despite the lack of public commitment, members of Vance's party here insisted that the secretary had made progess in private meetings today and expressed optimism that his urgings would result in a softer policy among five governments.

Vance arrived at a Bali Island resort near here last night for two days talk with foreign ministers of countries belonging to the Association of Southeast Asian Nations (ASEAN). The countries are Thailand, Malaysia, Indonesia, Singapore and the Philippines.

On Saturday, the ministers agreed in a joint communique "to take firm and effective measures" to prevent refugees from landing on their shores and indicated that they are planning coordinated patrols to stop the growing parade of refugee boats.

Their joint communique also warned they would send away refugees already ashore if they are not accepted for resettlement elsewhere "within a reasonable time frame."

The Vance mission was essentially a timebuying effort to induce two countries, Malaysia and Thailand, to stop pushing away refugees. Malaysia has been forcing Vietnamese refugees' boats back to sea for the past four months and Thailand recently forced thousands of Cambodian refugees back to their war-torn country.

He hoped to convice the ASEAN countries that a major international campaign is under way to take refugee off their hands and that they should moderate their policy until after in international conference is held in Geneva later this month.

Vance cited President Carter's recent pledge to double the number of refugees taken into the United States and the Tokyo summit conference's pledge to increase aid significantly as growing evidence that the international community is coming to their aid. Leaders of the five nations have complained in the past that the rest of the world offered only promises.

Japan added some more help today. Foreign Minister Sunao Sonoda announced here that his country would double its share of contributions to United Nations refugee organization, paying half the costs instead of the one quarter it now pays.

The new offers of support have been welcomed by ASEAN foreign ministers but they have pronounced them insufficient. Their communique Saturday was a kind of rebuke to the United States, since it did not mention Carter's promise to double from 7,000 to 14,000 the number of refugees permitted to resettle on American soil each month.

Both Thailand and Malaysia have strong domestic pressures to exclude refugees. State Department officials said they could not be expected to publicly reverse their position. "But the officials said they hope those two countries will quietly moderate their policies.

"We hope that they are prepared to do more privately than they will say publicly," said one high State Department official. "We hope that we can get commitments that they will be more responsive."

The officials were encouraged by the response tonight of Mochtar Kusumaatmadja, the Indonesian foreign minister, who said at a news conference that not all of the five nations take identical postions on refugees and that each is free, despite the tough communique, to act individually.

"Each of us will go home and consult with our government," Mochtar said, "taking into consideration what the communique says and what Mr. Vance has said." None of the ministers would venture be predict tonight what the reactions would be in their respective capitals.

Vance emphasized at a news conference tonight that promises of asylum in Southeast Asia would help obtain more funds for permanent resettlement from the U.S. Congress. Other U.S. officials were privately warning the five nations that Congress might react negatively to fund requests if its members continue to see vivid pictures of refugees being turned away from Malaysian shores.

Vance also sought to give some reassurance of U.S. support for Southeast Asian countries who fear new military adventures by Vietnam because of the Vietnamese-led invasion of Cambodia.

There is evident concern among ASEAN leaders that the Cambodian fighting will spill over into Thailand, causing a major war there, and that Vietnam ultimately wants to attack other countries in the region.

In a speech this morning, Vance asserted that the United States "is committed morally and by treaty to support the ASEAN states. We have made this clear to all concerned, and directly to the Soviet Union and Vietnam."

Questioned later about what that meant, Vance said he was making no new commitment and acknowledged that the United States does not have treaty commitments to all five ASEAN states.

The only commitment the United States has in this area is the Manila Pact, which embraces only Thailand and the Philippines. It pledges the United States only to consult with an attacked country, not to rush in with military aid.

Asked what the United States would do if Thailand were suddenly invaded, Vance said that question would be dealt with "when the time comes."

But he agreed, in his speech, that the Cambodian conflict "poses an increasingly serious danger to the security of the region." A high offical said the main concern now is not of an all-out Vietnamese invasion of Thailand but the possibility of fighting accidentally breaking out on the Thai side of its often disputed border with Cambodia. CAPTION: Picture, Vance talks with foreign ministers Rajaratman of Singapore, left, and Peacock of Australia. AP