BANGKOK, DEC. 31 -- Sixty-five Amerasian children and 91 accompanying family members arrived here from Vietnam today under a new emigration program negotiated in September between officials from the United States and Vietnam.

U.S. Ambassador to Thailand William A. Brown greeted the group at the airport, saying for translation, "This is going to be a very exciting new year for you and your new homeland as you get to know its people." Each emigrant was given a small American flag and a booklet titled "This is America."

Emigrants in their teens were dressed in western-style clothes and were accompanied by older family members, a few of whom wore traditional clothing. Under the program, the emigrants do not require a sponsor in the United States but enter on the same basis as immigrants from other areas.

Nguyen Thi Thu Nguyet, 21, who came from a small town in the Mekong delta with her husband and two sons, 6 and 4, said she left because "I would like to go see my father." She said she knew nothing about her father but thought his name was Louie. She had no idea where he was living now.

Vietnam stopped the refugee interviewing process for Amerasians and other Vietnamese seeking to migrate to the United States in January 1986. Hanoi complained that U.S. red tape had caused delays and a large backlog of applicants waiting to go. Hanoi and Washington, which do not have diplomatic relations, agreed to resume cooperation on humanitarian problems, including the Amerasian departure program, during a visit to Hanoi by presidential envoy Gen. John W. Vessey in August.

This was the first group to come out under the new bilateral program. Most of them were interviewed by U.S. immigration officials, who worked in Vietnam for the first time since the communists won the war in 1975.

Since the Orderly Departure Program for refugees began in 1979, the interviewing had been done by private Americans working for nongovernmental organizations and assigned to the United Nations High Commissioner for Refugees.

A few of the Amerasians interviewed at the Bangkok airport said they left because they faced prejudice as a result of their illegitimate, mixed-race birth. Most said they suffered economic hardship and many of those coming from Ho Chi Minh City, formerly Saigon, said they had survived by selling cigarettes, peanuts or lottery tickets.

"Life was very hard," said Ly Ngoc Diep, 22, who lived with his mother, stepfather, a brother and a sister on a small rice farm in Song Be Province in the southern Mekong delta. "And I had no chance to get a good education."

Diep, whose father was a black serviceman fighting in Vietnam during the war, said he did not know what he wanted to do when he got to the United States, although he hoped to finish high school. Diep came out alone.

Elizabeth Berube, deputy director of the American Orderly Departure Program office here, said about 3,800 Amerasian children and over 5,000 family members left Vietnam before the program halted two years ago.

Berube estimated that about 12,000 Amerasians remain in Vietnam and said the U.S. Embassy here has files on over 8,000 Amerasians asking to go to the United States.