Cambodian resistance forces battled Vietnamese troops at several points along the Thai-Cambodian border today amid reports of a successful guerrilla counterattack at a major Cambodian refugee settlement overrun by the Vietnamese in a Christmas Day assault.

Thai Maj. Gen. Sant Sriphen, commander of the Burapha (eastern) Task Force, told the Thai supreme commander, Gen. Arthit Kamlang-ek, in a briefing at the border today that about 3,000 Cambodian guerrillas of the anticommunist Khmer People's National Liberation Front had recaptured three-fourths of their Rithisen camp after a series of counterattacks this morning.

However, a Khmer front spokesman in Bangkok had no word tonight of such an operation. He said the front's guerrillas had never completely abandoned the camp -- although its 62,000 civilian population was evacuated -- and still held the northwestern portion of it. He said the Vietnamese reinforced their contingent in the camp today and now have a regiment there, backed by eight tanks.

The front spokesman, Bora Kanthoul, also reported sporadic Vietnamese shelling of the front's headquarters camp at Ampil, about 18 miles north of the Rithisen settlement. The Rithisen camp also is known as Nong Samet because it lies just across the border from the Thai village of that name. Yesterday, Ampil's 23,000 civilian population evacuated to an antitank ditch just inside Thailand in preparation for an expected Vietnamese assault.

According to western diplomats and Cambodian resistance sources, fighting is also going on between the Vietnamese and resistance groups in or around at least four other Khmer front camps and in the hilly Cambodian area of Phnom Malai, south of the Thai border town of Aranyaprathet, where the communist Khmer Rouge guerrillas have a major stronghold.

Elements of at least four Vietnamese divisions supported by tanks and artillery have been thrown into the fighting, diplomats said. The Vietnamese, who invaded Cambodia six years ago and ousted the brutal Khmer Rouge government, have approximately 160,000 to 180,000 occupation troops in the country protecting a hand-picked Cambodian government against 30,000 to 40,000 Khmer Rouge guerrillas, about 12,000 Khmer front troops and about 5,000 fighters loyal to the exiled Cambodian head of state, Prince Norodom Sihanouk.

While the current Vietnamese dry-season offensive appears no bigger than in previous years, there are indications that their logistics may have improved, permitting a more wide-ranging offensive and raising fears among Cambodians of a more sustained presence along the border.

"I have a feeling that the Vietnamese will try to hold their positions and stay in the camps" that they capture, said Bora Kanthoul. "That would keep us off balance."

"They may dig in and stay there" to keep the resistance camps' civilian populations on the Thai side of the border so that the Vietnamese "can show they control Cambodia," a western diplomat said.

In fact, diplomatic and resistance sources said, elements of the Vietnamese 5th Division have remained in positions just east of a lake bordering the Khmer front's Ampil camp since attacking it earlier this year. Although there has been no Vietnamese ground assault on Ampil so far during this November-to-May dry season, "they can do it at any time," a diplomat said.

By staying in forward, relatively well-supplied positions near Ampil and at other points along the 450-mile Thai-Cambodian border during an unusually light rainy season this year, the Vietnamese were poised to take advantage of early dry weather and launch their offensive more suddenly than in the past, diplomats said. The dry season usually favors movements of Vietnamese troops and equipment, while the monsoon season gives the guerrillas an advantage.

Vietnamese troops, reportedly with some help from a unit of the fledgling Phnom Penh government army that Hanoi is trying to build up, overran the Nong Chan camp of the Khmer front in November and burned much of it before withdrawing. The front says its forces have now reoccupied the camp, although about 20,000 civilians remain at evacuation sites in Thailand.

Another Vietnamese attack captured a Khmer front base at Sokh Sann on the southern Thai-Cambodian border. The Vietnamese are reported still occupying the camp, but fighting in the area is continuing, diplomats said.

The Rithisen, or Nong Samet, camp attacked Tuesday offered perhaps the easiest target and the greatest opportunity for disruption, as its 62,000 population lived in a geographically exposed position defended by the weakest of the Khmer front forces, diplomats said.

But the front also feels it is being targeted more than usual this season for political reasons because it offers the most attractive alternative to the Vietnamese-installed communist regime in Phnom Penh.

"We are the biggest obstacle to the Vietnamese in Cambodia," said Son Sann, the leader of the Khmer front, as he toured an evacuation site called "Red Hill" about two miles inside Thailand today. There, the 62,000 refugees from Rithisen are living under makeshift shelters of bamboo and plastic sheeting supplied by the U.N. Border Relief Operation, which is also providing food and drinking water.

"I feel we are being singled out this year," said Khmer front spokesman Bora Kanthoul, "because we've been getting stronger and the Vietnamese feel we present a threat to their hold of Cambodia."

While the Khmer Rouge remain the greatest military threat, "they are less important politically because the whole world abhors them," a western diplomat said.

Bora Kanthoul said that in the current offensive the Vietnamese appear to be targeting civilians more than before, shelling inhabited sections of Khmer front camps rather than military installations and planting land mines at one settlement along civilian escape routes.

He speculated that the Vietnamese could be trying to "discredit our forces as being incapable of protecting our civilians."

So far, there have been no precise figures for casualties in the current offensive. But resistance sources estimate that about 70 fighters and civilians have been killed and 200 wounded.