Klord Ang wept silently as she awaited an operation at this Red Cross hospital to graft skin from her legs onto her badly wounded right arm. After drying her tears with a scarf, the 24-year-old Cambodian refugee told her story.

She said she was trying to flee a Vietnamese attack on the refugee settlement of O Smach April 5 when she and a group of other Cambodians were intercepted by invading Vietnamese soldiers.

"The Vietnamese stopped us from running away," she said. "They made us go into a bunker, then they threw in three hand grenades." She said that "about 14" people were herded into the large bunker, none of them the guerrillas who are battling the Vietnamese occupation of Cambodia. She said that nobody was killed but that at least six persons were wounded.

Now Klord Ang fears that once she recovers she will face yet more danger on the Thai-Cambodian border. Thai authorities have begun sending Cambodian refugees, who fled the camp at O Smach to seek safety inside Thailand, back to a site on the border that is dotted with land mines.

Many of the Cambodians fear that they will again be exposed to the Vietnamese offensive because of a Thai decision to evacuate a refugee site well inside Thailand and place the O Smach refugees back on Cambodia's northern border with Thailand.

Nearly 30,000 Cambodians were sent to a new site at Ta Tum, about 12 miles east of O Smach, on Thursday. Yesterday the hospital here received 14 refugees who had been wounded by a land mine as they were moving to the new site. A woman and two children were killed in the blast, an official said.

Thai authorities refused to allow a reporter to visit the site where another land mine explosion was heard this afternoon. According to Thai officials who radioed for help, one person lost a leg in the explosion.

Because Cambodian refugees at this hospital are aware of the danger from land mines at Ta Tum and are afraid of being sent there, "all the people in the hospital don't want to go to Ta Tum," said Klord Ang. "But if they send us there we will have to go, because O Smach has Vietnamese soldiers."

Klord Ang's account of the Vietnamese assault on the O Smach camp tended to confirm charges by a Cambodian resistance leader that the Vietnamese rounded up civilians and killed some of them with grenades. But her story and other descriptions of the assault indicated that the Vietnamese were less intent on massacring Cambodian civilians than on terrorizing them. It remained impossible to establish a death toll from such incidents.

Son Sann, the head of the anticommunist Khmer People's National Liberation Front resistance group, has charged that Vietnamese troops "herded several hundred civilians--about 300 men, women and children--into ditches and executed them with hand grenades before finishing them off with bayonets." In an April 11 statement, he said he has asked the U.N. secretary general to investigate the "abominable massacre by Vietnamese occupation forces."

While survivors of the attack have confirmed elements of Son Sann's charges, none has mentioned the use of bayonets by Vietnamese troops, and doctors at the Red Cross hospital here say they have noticed no wounds consistent with bayonet stabs.

Most of the 44 wounded patients here from O Smach were injured by artillery shells or land mines, doctors said. Perhaps 10 to 12 were wounded by grenades, they said.

"If there was a manifest intention to massacre people, there would have been more wounded," said one relief official. "You can't compare this to Shatila, Sabra or Assam," he said, referring to massacres of civilians in Lebanon and India.

Nevertheless, it is clear from the refugee accounts that the Vietnamese targeted unarmed civilians after breaking through the O Smach camp's meager defenses. The tactic of forcing civilians into bunkers and throwing grenades in after them is known to have been used during the Vietnam war when the communist forces captured villages that were solidly supportive of the South Vietnamese government.

In the case of O Smach, refugees reported similar grenade attacks on different parts of the sprawling camp on three separate days.

One survivor, Ngat Mao, 37, told an interviewer today of an attack April 3 in which about 70 Vietnamese troops overran his village within the camp after an artillery barrage. He said the Vietnamese at first made him and 18 other civilians come out of the horseshoe-shaped bunker where they had taken refuge from the shelling, then made them go back in again.

Ngat Mao said the Vietnamese then threw two canister-like grenades into each end of the bunker, wounding seven persons, including his wife and son.

At that point, he said, resistance guerrillas loyal to exiled Prince Norodom Sihanouk launched a two-pronged counterattack, killed two of the Vietnamese and wounded one, who was captured.

The wounded Vietnamese was taken out of the Kapchoeng Hospital today by Thai military intelligence officers and driven in a Red Cross ambulance to the Thai border town of Aranyaprathet, where he was to be detained with several other Vietnamese prisoners captured in the current offensive against Cambodian resistance settlements.

According to refugees at the hospital, not all of the Cambodians who were wounded by grenades had been herded into bunkers. Some apparently were already huddling in the bunkers when the Vietnamese overran the camp.

Em Polah, 24, said that in some places the Vietnamese ordered people into the bunkers and that in other places the Cambodians, including some resistance fighters like himself, were in the bunkers to take shelter from the shelling. He said he saw Vietnamese soldiers throw a grenade into a bunker holding five people, some of whom were killed or wounded. But he said he did not see any Vietnamese using bayonets. He said he believed that more civilians than soldiers were killed and that many of them died from stepping on land mines as they were fleeing.

Em Polah said he was wounded by gunfire as he was running away from a bunker to escape a Vietnamese assault.