Secretary of State George P. Shultz received a hero's welcome from displaced Cambodians at the Thai-Cambodian border today but avoided a clear response to an emotional plea for greater U.S. support for their battle against Vietnam.

Shultz received the plea in a bamboo-and-thatch hut six miles inside Thailand that serves as administrative headquarters for 55,000 Cambodians driven out of a border camp by Vietnamese attackers last Dec. 25. Outside the hut, thousands of Cambodians lined the paths and roadways of the camp chanting "U.S.A. -- Number One" on cue from cheerleaders and holding signs in English appealing for guns, education and other U.S. aid.

Thou Thon, administrative chief of the camp, known as Evacuation Site 7, appealed to Shultz to support $5 million in proposed aid to the noncommunist Cambodian resistance currently pending in amendments before Congress. Site 7 is organized and led by the Khmer People's National Liberation Front, a noncommunist group headed by former Cambodian premier Son Sann.

Shultz replied that the United States will continue to supply "tangible financial assistance" to the Cambodians but avoided any mention of U.S. military assistance, which is being advocated by some.

Questioned by reporters later in a news conference in Bangkok, Shultz endorsed economic and humanitarian support for the Cambodians but again sidestepped the question of military aid. If the $5 million is provided by Congress, Shultz added, the funds could be spent to meet "economic needs."

He declined to comment on a Washington Post report this week that the Reagan administration has been providing secret U.S. aid to the noncommunist resistance since 1982.

Shultz said his helicopter-borne tour of the border area, which took place under very heavy Thai military security, provided a new dimension to his appreciation of the "human tragedy" arising from the Vietnamese occupation of Cambodia.

In such a firsthand visit, he said, "You take into your gut what you knew in your head" from secondhand reports of existing conditions.

Shultz's six-hour field trip also included visits to a Thai military post three miles from the Vietnamese border and to a nearby village housing Thais who have been driven out of border area homes. He also went to a processing camp for Cambodian, Vietnamese and Laotian refugees hoping to emigrate to the United States and other countries.

Shultz is the highest ranking U.S. visitor and the first secretary of state to visit the Thai-Cambodian border area since it became a cockpit of military conflict and refugee movements caused by the Cambodian war.

About 230,000 Cambodians were driven out of border camps and pushed back into Thailand by a Vietnamese military offensive late last year and this year. About 60,000 are organized by the Communist Khmer Rouge faction headed by Pol Pot, according to a U.S. Embassy official, but the rest of the evacuees are led by noncommunist groups.

The Communist Khmer Rouge, who are held responsible for millions of deaths by execution and starvation during their 1975-78 domination of Cambodia, led the largest guerrilla force attacking the Vietnamese occupation. The Khmer Rouge, supported mainly by China, have been condemned rhetorically by the United States but nevertheless continue to be tolerated by Washington as a member of the anti-Vietnamese coalition, which Washington supports as the occupant of the Cambodian seat in the United Nations.

China, in addition to supporting the Khmer Rouge, provides about two-thirds of the military support received by the noncommunist insurgent groups led by Son Sann and Cambodia's former chief of state Norodom Sihanouk, according to a knowledgeable western diplomat.