A U.S. senator's complaint that Thailand was forcibly turning back refugees from neighboring Laos has drawn sharp criticism from the Thai national security chief and underscored a growing strain on the country's refugee policy.

Prasong Soonsiri, the secretary general of the National Security Council and Thailand's leading policy-maker on refugees, acknowledged that authorities along the Thai-Laotian border had turned back people attempting to cross, but he said they were not "real" refugees. He denied that any of the Laotians had come under fire from Thai border forces.

Prasong was reacting to a complaint by Sen. Mark Hatfield (R-Ore.), who wrote to Secretary of State George P. Shultz to demand an investigation of reports that Thai forces had turned back, and even shot at, Laotians fleeing the Communist government in Vientiane and seeking asylum in Thailand.

Hatfield's letter to Shultz urged his "intervention in obtaining timely and accurate reporting on this life-threatening problem and what the United States is doing to moderate the Thai policy."

The complaint focused attention on a refugee problem that Thailand considers more serious than the current presence of 250,000 Cambodians who have fled an offensive by Vietnamese troops against Cambodian resistance camps.

The Laotian refugees are a mixture of lowlanders and hill tribesmen, including members of the Hmong tribes that fought for the CIA against Communist guerrillas in Laos during the Vietnam war. A major difficulty with the turning back of Laotians, from the point of view of western refugee officials, is that there is currently no procedure to screen those who may be fleeing persecution for their past ties to the United States.

According to the Office of the U.N. High Commissioner for Refugees (UNHCR), there are now about 86,300 Laotians in Thai refugee camps near the border with Laos.

While Thai authorities expect the Cambodians to return to their side of the border eventually, the number of Laotians in the Thai camps has been growing steadily with practically no hope of resettlement in other countries or voluntary return to Laos, refugee officials said.

Prasong said Thailand was maintaining its policy of providing temporary asylum to refugees fleeing political persecution, but not to those seeking a better life abroad. He compared the turning back of "illegal entrants" from Laos to the repatriation of Mexicans and Cubans by the United States.

Prasong complained that Thailand was being stuck with a growing Laotian refugee burden since foreign countries, notably the United States, were applying strict conditions for taking in refugees and accepting far fewer than before.

In an interview yesterday, he said that if Sen. Hatfield "can convince the U.S. government to receive these people, I will invite him to come with me to the Mekong River to welcome them."

He added, "If people in the United States would like to receive Laotians, why not set up an Orderly Departure Program in Laos to let them go and settle in your country legally?" He referred to a U.N.-sponsored program established in Vietnam to provide a legal outlet for refugees and cut down on illegal, dangerous departures by Vietnamese "boat people."

A UNHCR official said the agency now is working with the Thai government on establishing a screening procedure so that Laotians fleeing for political reasons can be separated from those who do not qualify as refugees.