Anticommunist Cambodian guerrillas today resumed a drive to dislodge Vietnamese troops from a resistance camp near the Thai-Cambodian border but appeared to lose ground in a heavy Vietnamese artillery barrage, according to Thai military sources.

At least two guerrillas of the Khmer People's National Liberation Front were reported killed and 30 wounded in today's fighting at the resistance group's Rithisen camp on the western Cambodian border opposite the Thai village of Nong Samet after a relative lull yesterday. Front officials here had no information about the reported loss of territory recovered earlier in the drive to recapture the camp from the Vietnamese. But they acknowledged having lost about 50 guerrillas killed and 200 wounded in eight days of fighting, marked by some of the heaviest Vietnamese shelling of the six-year-old Cambodian war.

Front officials said Vietnamese casualties were even higher, but they had no reliable figures. In one guerrilla thrust at the camp, officials said, 40 Vietnamese medical personnel were killed while trying to recover wounded soldiers.

Fighting between Vietnamese troops and Khmer front guerrillas was also reported today at the O Bok resistance base on the northern Cambodian border.

In another incident south of the Thai border town of Aranyaprathet, Thai troops clashed briefly with about 20 Vietnamese soldiers who reportedly crossed the border from Cambodia in pursuit of guerrillas, Thai authorities said. There were no Thai casualties, and Vietnamese losses were unknown, they said.

At the Khmer front's headquarters at Ampil, 18 miles north of the Rithisen camp, Vietnamese gunners fired artillery shells on the camp's defensive perimeter, Thai reports said.

Thai military sources said that in the fighting today at the Rithisen camp, which was overrun by the Vietnamese Dec. 25, about 3,500 Khmer front guerrillas involved in the battle apparently failed to dislodge Hanoi's troops in the face of reinforcements and withering artillery fire.

One Thai military officer told reporters at the border that the guerrillas now hold about one-fifth of the Rithisen camp, down from one-third yesterday. Khmer front officials have said their forces recaptured three-fourths of the camp in fierce counterattacks in the last week.

When the Vietnamese assault began on Christmas, about 62,000 Cambodian civilians were quickly evacuated from the camp, the largest operated by any of the three guerrilla groups opposing the Vietnamese occupation of Cambodia.

Since Vietnam's current dry-season offensive began unexpectedly early on Nov. 18, about 110,000 Cambodian refugees have been forced to flee their resistance settlements along the border and cross into Thailand for safety. Casualties in these evacuations have reportedly been minimal.

However, the prospect that the Vietnamese may try to hold the resistance camps they overrun, instead of withdrawing after having burned them as in previous years, has alarmed Thai authorities.

In an interview published today by the Bangkok Post, Thai National Security Council chief Prasong Soonsiri also expressed concern that a growing Soviet military presence in Vietnam might lead to Moscow's intervention in Cambodia if the Vietnamese proved unable to subdue the resistance forces.

Prasong said the Soviets have increased their air power in Southeast Asia by stationing 14 MiG23 fighter planes at Cam Ranh Bay in southern Vietnam for the first time.

He told the paper the planes threatened the peace, security and stability of Southeast Asia's noncommunist countries and served to draw Vietnam more closely into the Soviet orbit.

Prasong also said the Soviets in November increased to 16 the number of their Tu16 medium bombers based at Cam Ranh Bay, a military facility originally built by the United States. He said that as part of the Soviets' stepped-up air power at the base, eight Tu95 surveillance planes and Tu142 antisubmarine patrol planes were also stationed there.