Thousands of refugees flocking from Indochina to escape the social and political upheaval in that region are converting the vast, sparsely inhabited Northern Territory of Australia into a new Asian enclave.

It is an unlikely development, since for all but the last half dozen years of this century, Australia adhered to an immigration policey that excluded virtually all non-Europeans.

The country officially dropped its "white Australia" policy early in the 1970s and has been admitting token quotas of Asians, mostly young people who studied at universities here and married Australian-born students.

The shift in policyis closely linked to the war in Vietnam, in which Australia was a close ally of the United States and South Vietnam. Since the war ended, Australia has accepted 15,000 Indochinese refugees - mainly Vietnamese - and is now admitting them at the rate of 10,000 a year.

Immigration Minister Michael MacKellar claimed this week that "as a proportion of Australian population, this intake represents an effort larger than that of any other refugee-receiveing county."

The United States has been taking about 25,000 refugees a year and is seeking to increase that figure by 22,500 this year. France has admitted about 45,000 since the Vietnam war, and Canada and West Germany also have opened their borders more recently to a number of Indochinese refugees. Still, tens of thousands of refugees are awaiting resettlement, mostly in primitive camps in Thailand and Malaysia.

The United States has a population of 215 million, compared to Australia's 13.5 million and France's 55 million.

About half the refugees in Australia have gone to the major cities of Sydney, Melbourne and Adeliade, in the nation's temperate southeastern corner. But the rest have entered through the rough-and-tumble town of Darwin, capital of the Northern Terriotry and a city closer to most of Asia than to most Australians.

Nearly 2,000 of the refugees who have arrived in Darwin are "boat people" - refugees who ahve bought or badgered their passage from Southeast Asia on small, oftern unseaworthy boats.

There has been much controversy about the boat people in Darwin, and antagonism toward them. With Australia's unemployment rate running at record levels of between 6 and 7 percnet, unions in Darwin are strongly opposed to the boat refugees being admitted into Australia.

Elsewhere in the Northern Territory, however, they are welcomed and many have already started to work as farmers. The Northern Territory is the last section of the great Australian outback.

Spreading over more than half a million square miles of land that ranges from tropical swamps in the far north to a harsh, pastel-colored desert around the central town of Alice Springs, the teriotory has a population of only 100,000.

It also the largest concentration in Australia of the nomadic aboriginals, with nearly 30,000 of Australia's indiegnous black people living in settlements, roaming the countryside and demanding an increasingly large share of the profits from the territory's rich uranium deposits.

Last July, the territory took its first major step toward statehood by the end of this century. The federal government in Canberra gave it a degree of self-government only a little short of full statehood. Young Conservative Paul Everingham, 34, became the territoryhs first chief minister and the driving force behind a plan to settle more and more refugees in the territory.

The plans are full of hazards in a county with Australia's racial history. Apart from imposing a complete ban on nonwhite immigration beginning in 1901, when it became fully independent of Britain, Australia expelled tens of thousands of Chinese and South Sea islanders in the latter part of the 19th century. The history of white Australia's treatment of the aboriginals is a bleak chapter in the nation's history.

Even though the movement of Indo-chinese refugees to Australia is still in its infancy, it is already the biggest Asian influx into Australia this markably little public oppostion, doubts and fears remain only a scratch below the skin of Australian consciousness.

A recnet opinion poll showed that 80 percent of Australians opposed further immigration of Asians. The Australian government has committed the country to take more Indochinese refugees at the current rate, but is doing its best to keep the whole question and its problems away from the public spotlight.

Immigration Minister MacKellar said this week that the Indochinese refugees who had arrived so far in Australia "had integrated very well."

"I would not say for a moment that there has been widespread antagonism, but there has been community concern about the arrival of unauthorized boats carrying refugees," he said.

"There is a concern about the risk to public health and about the possible introduction of exotic plant or animal diseases."

Whether that concern spreads into a broader prejudice against the new wave of Asian immigration is one of the government's deepest concerns. Canberra is nervous that Australians will revive their old reputation for racism and thus immesely damage Australia's relations with her Asian neighbors. At the same time, officials are increasingly interested in quietly encouraging Asia migration-quite apart from refugees-to fill more of the empty land in Australia's "Asian" north, but to do it without alarming the country's white population.