PHETCHABUN, Thailand - Thai troops packed more than 4,000 ethnic Hmong into military trucks yesterday for a one-way journey to Laos, all but ending the Hmong's three-decade search for asylum after their alliance with the United States during the Vietnam War.

The United States and rights groups have said the Hmong could be in danger if returned to the country that they fought, unsuccessfully, to keep from falling into communist hands in the 1970s.

Although Thai soldiers were armed yesterday with batons and shields, Col. Thana Charuwat said no weapons were used in the repatriation and said the Hmong offered no resistance. The last of the group is expected to cross the border early today.

Many Hmong, an ethnic minority from Laos' rugged mountains, fought under CIA advisers during the Vietnam War to back a pro-American Lao government - Washington's so-called secret war - before the 1975 communist victory.

Some former American soldiers and civilians who developed close bonds with the Hmong during the war think the United States should have done more to help them.

Since the war, more than 300,000 Lao, mostly Hmong, are known to have fled to Thailand and for years were housed in sprawling camps aided by international agencies. Most were either repatriated to Laos or resettled in third countries, particularly the United States. Smaller numbers found refuge in France, Australia, and Canada.

But now Thailand says it plans to close the camp it emptied yesterday. That leaves only about 150 Hmong asylum-seekers known to remain in the country. They are kept in a prison near the Lao border, and some have threatened suicide if they are returned to Laos.

The Thai government contends that most of the Hmong are economic migrants who entered illegally and have no claims to refugee status.

New York-based Human Rights Watch yesterday called the deportation "appalling" and a low point for Thai Prime Minister Abhisit Vejjajiva's government.

U.S. State Department spokesman Ian Kelly said the United Nations and Thailand in the past had deemed that many of the Hmong in this group were "in need of protection because of the threats they might face in Laos."

"The United States strongly urges Thai authorities to suspend this operation," Kelly said in a statement.

Abhisit, however, said that Thailand had received "confirmation from the Lao government that these Hmong will have a better life."

The Hmong were driven out of the camp in military trucks and were to be put on 110 buses going to the Thai border town of Nong Khai. Once in Laos, they will head to the Paksane district in the central province of Bolikhamsai, said Thana, the Thai army's coordinator for the operation.

Thana said 5,000 soldiers, officials, and civilian volunteers were involved in the eviction.

One rights group said callers from the camp had reported violence and bloodshed. Thana denied the allegation.

"There has been no violence, and nobody has been injured," Thana said. He said it was impossible for anyone in the camp to call outside because the military had jammed cell-phone signals.

Journalists and independent observers were barred from the camp.

Laos Foreign Ministry spokesman Khenthong Nuanthasing rejected international concerns, saying the government has a "humanitarian policy" for resettling the Hmong.

He said they would initially be placed in a temporary shelter, then housed in two "development villages," where each family would receive a house and a plot of land that international observers would be welcome to inspect.