The plight of 2,500 sick and hungry Vietnamese refugees who have been stranded for more than a week on an old freighter off the coast of Malaysia has sharpened international concern over a new floodtide of homeless refugees in Southeast Asia.

The wanderings of the freighter Hai Hong, carrying the largest human cargo yet of refugees fleeting Vietnam by water, has created a new sense of urgency in Washington, State and Justice Department officials, under pressure from Congress conferred yesterday about possibly enlarging the U.S. program for taking in refugees under emergency immigration procedures.

The United States and the U.N. High Commissioner for Refugees also strongly urged Malaysia to give temporary sanctuary to the Hai Hong's occupants. Later yesterday, the French government announced that it would accept any of the refugees who wanted to go there an either spoke French or had relatives in France.

But Malaysia, which has already been inundated by tens of thousands of "boat people," continued last night to refuse to allow the people on the Hai Hong to come ashore. Malaysia agreed only to help repair the 1,500-ton freighter's engine and to provide food, water and medicine to its 2,518 occupants, described by an American television reporter who visited the ship as suffering from hunger in "really bad" overcrowded and filthy conditions.

Malaysia's population is made up of ethnic Malays, Indians and ethnic Chinese and there often has been friction among the groups. Some observers speculated that the Malaysian government could face internal political problems if it admitted a large group of ethnic Chinese refugees.

There have been reports that the ethnic Chinese leaving Vietnam have sufficient means to pay Vietnamese officials for safe exists and to pay boat captains for transporation. Officials here said yesterday that Vietnam may be encouraging the exodus of a potentially troublesome ethnic minority and a merchant class willing to leave much of their wealth behind.

The Malaysian government questioned whether the Hai Hong's occupants mostly ethnic Chinese from Saigon's old commercial quarter of Cholon, were genuine refugees because they were believed to have paid as much as $5 million in gold and U.S. dollars to a Hong Kong syndicate for the ship to pick them up from the coast of Vietnam.

But officials in Washington and at the United Nations said they believe the Malaysian government simply does not want to add so many more refugees to the 35,000 or more already in camps on the Malaysian coast, awaiting permanent homes in other countries under arrangements being coordinated by the U.N. High Commission.

"They are up to their needs," one U.N. official said of the Malaysians' refugee problem, "and they don't seen and end."

Some officials in Washington said they believed Malaysia could be persuaded to give temporary sanctuary to more refugees if the United States, among other countries, moved faster to take them out of Malaysia and give them permanent homes.

In a statement issued by his Washington office, Sen. Edward M. Kennedy (D-Mass), urged the U.S. government o expand the quota of Southeast Asian refugees it will allow into the country and to speed up its processing of refugees alreadly assured places here.

Kennedy said the United States must "take new steps to assure Malaysia and other countries in Southeast Asia that America's door is still open for the resettlement of homeless refugees." He urged Attorney General Griffin Bell "to extend the parole authority to meet the emergency resettlement needs among boat refugees and to dispatch immigration officers to Kuala Lumpur, the capital of Malaysia, to expedite the processing of additional boat refugees for resettlement in the United States."

Under special authority from Congress, the attorney general has given emergency "parole" entry to a maximum of 25,000 Southeast Asian refugees now in camps in Malaysia and Thailand. Refugees with relatives here or former ties to the U.S. government during the Vietnamese war have priority.

No government official was able to say yesterday how many of these 25,000 refugees have been identified for immigration to the United States. A State Department spokesman said that only 3,500 are know to have arrived in this country thus far.

Justice and State Department officials conferred all day yesterday about either enlarging the 25,000-refuge quota or extending it beyond the current fiscal year. A Justice spokesman said last night that no decisions had been reached on those or other options, but he said the House and Senate Judiciary Committees would be consulted before the attorney general takes any action.

Congress already voted, before the end of its last session, to urge Attorney General Bell to create an additional emergency entry quota for several thousand refugees fleeing Cambodia. Bell has not yet acted on that either.

As recently as this past summer, these numbers seemed sufficient to fulfill the American obligation to homeless refugees from the years of upheaval in Southeast Asia. The outflow of refugees was believed to be slackening.

Against a background of friction between Vietnam and China, however, ethnic Chinese who made up a large merchant class in Vietnam before the war began fleeing in large numbers, some to China and others to Malaysia by water, joining other Vietnamese boat people.

Refugees from the harsh new regime in Cambodia and war-torn areas of Laos also continued streaming into Thailand where there are now an estimated 130,000 people awaiting resettlement. Vietnam itself, now in armed conflict with Cambodia, also is being inundated with refugees from Cambodia.

At the suggestion of Secretary of State Cyrus Vance, the U.N. High Commission has scheduled an emergency internation conference in Geneva next month to seek action on the refugee problem.

About 30 nations, including Vietnam and others who received refugees in Southeast Asia, are being invited.The voyage of the Hai Hong and the new refugee emergency has dominated this week's meeting of the U.N. General Assembly's 15-nation social, humanitarian and cultural committee.

The "boat people" have exacerbated the refugee problem because of the great danger they face in often small or badly outfitted craft on the high sea. Many have already drowned or died of illness after weeks adrift.

As a result, the United States, France and other countries have immediatedly accepted refugees picked up by ships of their national registry and have given greater attention to them than to the refugees already living in camps in Malaysia and Thailand.

According to a Wall Street Journal account of the Hai Hong's journey, it is at least the second such freighter apparently operated by Asian entrepreneurs to make a prearranged pickup of ethnic Chinese refugees from Vietnam in exchange for payments in gold.

One official in Washington said the U.S. government has intelligence reports that there may be more such ships already loaded with refugees on their way to Malaysia.