After a year of lobbying by western governments and relief agencies, Thailand has relented on its policy of detaining more than 1,800 Vietnamese refugees in a squalid and dangerously situated camp on the Thai-Cambodian border as a deterrent to new arrivals.

In an interview, the head of Thailand's National Security Council, Squadron Leader Prasong Soonsiri, confirmed that the government has declared the Vietnamese eligible for resettlement abroad and has quietly begun allowing officials from the United States and other countries to process them for immigration.

Among the 1,890 detainees at the overcrowded camp, called NW82, are five Amerasian children fathered by Americans during the Vietnam War, U.S. officials said. Known as "land people" to distinguish them from the "boat people," the Vietnamese reached the Thai border by making a hazardous overland trip across embattled Cambodia.

To discourage others from making the trip and contributing to what Thai officials fear will be an "endless flow" of Indochinese refugees, the government since 1981 has practiced a policy it calls "humane deterrence," whereby arrivals from Vietnam and Laos are put into austere camps and denied eligibility for resettlement.

In the case of camp NW82, however, "it's been more on the order of inhumane deterrence," one refugee official said. Built for about 800 people, the camp, located 15 miles northeast of the Thai town of Aranyaprathet, has grown severely overcrowded as Vietnamese have continued to trickle in. In addition, refugee workers have complained of rampant disease, often insufficient food and water supplies, poor sanitation and occasional beatings and rapes by Thai guards.

Moreover, the camp, enclosed by a stockade of bamboo and barbed wire, sits in the middle of the Cambodian refugee settlement of Nong Samet, whose potentially hostile population of more than 40,000 is controlled by noncommunist Cambodian resistance groups opposed to the Vietnamese occupation of Cambodia.

Thai authorities have been sensitive about criticism of NW82, described by some visitors as more like a prisoner-of-war camp than a refugee facility. Last year a correspondent for the Asian Wall Street Journal was expelled for several weeks for writing about NW82, and in November Thai officials were angered when visiting U.S. Rep. Harold Sawyer (R-Mich.) deplored both the camp and Thai policy.

Sawyer called conditions at the camp "extremely poor" and said he would press for the release of the five Amerasians. He said he understood but could not accept the "humane deterrence" policy, adding, "I don't think Congress will accept it either."

Now, according to refugee officials, the change in Thai policy on the camp has put the onus on the United States and other western countries to take in the stranded Vietnamese.

"There is some worry now that the resettlement countries won't come through," one western official said. "It's the moment of truth. It's a question of putting their money where their mouth is."

Prasong said the government would close NW82 once the western countries had taken all the refugees deemed eligible for their programs. If any remain, he said, they will be put into the border camps among the Cambodians, where they are technically outside the responsibility of the Thai government.

Prasong said the policy shift affected only camp NW82 and that another 600 Vietnamese living at what relief officials call "exposed sites" along the border will have to stay where they are. The sites include hospitals at the Nong Samet and Nong Chan Cambodian refugee camps controlled by anticommunist resistance groups and the Phnom Chat camp run by the feared Khmer Rouge Communist guerrillas, who ruled Cambodia brutally until ousted by the Vietnamese four years ago.

Prasong insisted that the "humane deterrence" policy remains in force and said he does not expect the NW82 decision to bring a new influx of Vietnamese. He said that for the time being more than 7,000 Vietnamese boat people who arrived after the humane deterrence policy took effect would continue to be held at the Sikhui camp about 110 miles northeast of Bangkok, and more than 19,000 Laotian refugees would remain at the Na Pho camp in northeastern Thailand.

Prasong said that any new Vietnamese overland arrivals would be denied entry to Thai camps and would have to stay along the border with the more than 200,000 Cambodian refugees living there.

"If the Vietnamese want to resettle in a third country, they should go by orderly departure," he said, referring to the U.N.-sponsored program to fly out Vietnamese emigrants from Ho Chi Minh City. "Why should they risk their lives by walking across the country or sailing in the sea?"

Prasong said the Thai policy has cut arrivals of Vietnamese boat people in Thailand by 50 percent. But it apparently has had no discernible effect on arrivals of "land people," who continued to appear at the border at the rate of 60 to 80 a month last year while the policy was in force.

"People will continue to come; that's a fact of life," said a U.S. official. "Hopefully the number will be small and acceptable to the Thais."

He said he feared that a large new influx might cause the government to reconsider its relaxation of the policy, foreclosing the prospect of extending eligibility for resettlement to other refugees now stuck in limbo in "humane deterrence" camps.

Since the Thais gave foreign embassies permission last month to start screening the Vietnamese at NW82, officials from the United States, Australia, Canada, Malaysia and Finland have begun interviewing them, and France, West Germany and Denmark have agreed in principle to take some in, refugee sources said.