The dirt road north of Bien Hoa leads past plantations of rubber trees and fields of manioc and peanuts. Then it gives way to barren scenes in what was once a "free-fire zone," land pocked by ash-gray bomb craters and some of it denuded by defoliants.

At the end of the road, men and women toil in fields trying to coax such crops as green beans and sugar cane out of the apparently unyielding soil. They are not very good at it, and the Vietnamese authorities do not hide their displeasure.

They do not want to be here, nor do the Vietnamese want them in the country. They are Cambodians of mostly ethnic Chinese origin, and they constitute Vietnam's own refugee problem.

Nearly 30,000 Cambodians have remained in Vietnam since fleeing their homeland after the communist Khmer Rouge took power in 1975 and instituted nearly four years of brutal, destructive rule. They have no desire to return. Most want instead to resettle in western countries. The Hanoi government is only too eager to see them go.

But they are stuck in the middle of a political conflict between Vietnam and the West. Western countries view Vietnam as the cause of a great and disruptive exodus, and they are less than enthusiastic about bailing Hanoi out of its own refugee troubles.

According to Vietnamese officials, about half the Cambodian refugees live in five remote camps in southern Vietnam and half remain in Ho Chi Minh City, formerly Saigon, where they originally gathered after fleeing their homeland.

Slightly more than 5,400 live in two adjacent camps here in a former Viet Cong-controlled area of Song Be Province, about 90 miles north of Ho Chi Minh City.

Asked at the camp's bamboo-and-thatch meeting hall during a recent journalists' visit whether they wanted to live abroad, all the Cambodians present raised their hands. They said they had sent applications for 500 families to U.S. authorities but had received no positive reply. Most inhabitants reportedly want to go to France, but the government there is none too keen either.

According to Do Duy Lien, the vice president of Ho Chi Minh City's governing "people's committee" and director of the local social welfare department, "We would like all 30,000 to be resettled, but if not, we will still take care of them."

In an unusual speech, she told visiting journalists, "We have to deal with social vices including prostitution in the city and the social vice of drug-taking. We encounter this problem in thousands of cases. There are thousands of invalids wandering around the city begging for support. There are children without roofs over their heads wandering about the city without families. There are thousands of orphans of mixed blood.

"We were just liberated, and therefore the situation of the city is still difficult," she said. "Adding to our burdens, we have to receive over 30,000 Khmer refugees. Once these people are in their houses, it is not simple to convince them they have to produce to ensure their livings. We have to deal with too many difficulties already without refugees. So we should do our best to permit their resettlement in third countries."

Lien also expressed concern about declining international aid for the Cambodian refugees. In 1982 the office of the United Nations High Commissioner for Refugees donated $1.1 million. This year the figure dropped to $900,000.

"For political reasons it's almost impossible for us to find money for Vietnam," said a UNHCR official. "And there's not a single dollar from Eastern Europe" for the refugee aid. "The ones who pay the price are the refugees."

At the Minh Tan meeting hall, a Vietnamese official proudly listed the camp's facilities: a sawmill, a school, a clinic, 160 barrack-like bamboo-and-thatch houses and a number of wells. But agriculture has not been as successful as hoped, the official added, because of "problems of the weather and the enthusiasm of the people taking part in production."

A Cambodian spokesman complained publicly, "We've been living in this camp for four years, and today we have one problem: Every month we get only 9 kilos 20 pounds of rice each, which is not sufficient."

"Our great hope is to rejoin relatives in third countries, because we have no more families or ties in Cambodia," he said. "We have no more homes or belongings there."

However, only about 8,000 of the 30,000 refugees are said to have relatives abroad, and even at that level, the rate of resettlement has been slow. In February, 96 left Vietnam; 62 were accepted the month before.

"It's a little difficult to take refugees who are in Vietnam as a country of first asylum when there are so many others who fled Vietnam," said a U.S. official in Bangkok. "Here is a country which is the source of a refugee problem and which has created problems for your friends. Shouldn't you help your friends first?"