Vietnam appears to have pulled its troops back closer to its borders after puntitive strikes deep into Cambodia, and the fighting seems to be cooling down, Western Indochina specialists said yesterday.

Attempting to pierce the fog of Cambodian claims of a "great victory" over Vientamese forces that were admittedly vastly superior, outside observers speculated that the Vietnamese have withdrawn partially from Cambodia, to await negotiations.

Amercian diplomats saw "straw-in-the-wind" indications that China, Cambodia's leading supporter, wants to strike a more even balance between Vietnam and Cambodia, perhaps to enocurage negotiations. Peking earlier this week said it signed a new trade agreement with Vietnam, which Cambodia has been accusing of "wanton aggression."

"Press accounts from Bangkok, Thailand, where Vietnamese Foreign Minister Nguyen Duy Trinh is visiting, reported yesterday that fighting in Cambodia "has virtually ceased" and that the Vietnamese, not the Cambodians, "were clearly the victors."

American sources, however, said U.S. intelligence, which is also the basis for much of the Thai military intelligence, is "too fragmentary" to reach conclusive judgments of what has happened in Cambodia. "The fighting has pretty clearly diminished," said one American source and the Vietnamese have pulled back, "but we don't have any independent confirmation that they have left Cambodia - we doubt that."

A Vietnamese source close to the Trinh delegation in Bangkok said yesterday: "We have no intention of seizing Phnom Penh (Cambodia's capital) or any Cambodian province." Thailand and Vietnam yesterday signed aviation and trade agreements. Vietnam has been anxious to show that it is continuing its normalization of relations with other nations, and it appears highly embarrassed by the publicity surrounding the border warfare with Cambodia. While both are communict states, Cambodia's brand of communism is far more extreme than Vietnam's. Cambodia has reportedly wiped out most of its educated classes since the Communists gained power in Phnom Penh in 1975.

Cambodian forces have also been involved in a series of bitter clashes on the Thai border.

At the same time, despite the border warfare with Vietnam, Cambodia currently is displaying a desire to redress its image of a bizarre, self-isolated society. Although foreign diplomats say Cambodia keeps the nine foreign missions in Phnom Penh in virtual "house arrest," except for the Chinese, Cambodia this week is receiving visits from six ambassadors accredited in Peking. They are the ambassadors of Sweden, Denmark, Finaland, Nepal, Tanzania and Mali.

Cambodia yesterday continued a campaign of radio broadcasts designed to counter Vietnam's charges that Cambodia initiated the border warfare by encroaching on Vietnamese territory. In the process, Cambodia also pursued its pattern of accusations against the Soviet Union.

In the fighting since last September, Cambodia charged that "aggressor Vietnam used hundreds of Soviet tanks, hundreds of artillery pieces and several army divisions to break through the thin defense line that Cambodia had left as a token force to defend its bor der."

Cambodia repaeated its calims that it has "routed . . . beaten and dispersed" these superior forces. It also acknowledged however, that some remain. A Phnom Penh broadcast said "mopping up operations" are continuing, "to wipe out all the remnants of the enemy still clinging to our territory in some border areas."

Not until all Vietnamese troops are out of its territory, Cambodia has said, will it be prepared to negotiate.

But current Cambodian statements might be construed as a prelude to negotiations, and one American specialist sadi yesterday, "for all we know, negotiations may be under way now."

Cambodia stressed yesterday the underdog nature of its relationship to Vietnam, and said that although "large chunks of Cambodian territory have been lost for generations as a result of Vietnam's aggression, expansion and annexation, the Cambodian people have no intention of digging up old accounts."

"Cambodia is a small country with a population of nearly 8 million people," the broadcast said, while "Vietnam, almost twice the size of Cambodia, has a population of more than 40 million people. The Vietnamese armed forces, more than 1 million strong, are equipped with modern Soviet tanks, modern Soviet artillery pieces and other modern Soviet weapons."

"Never in history," Cambodia claimed, "has a small country provoked a big country and commited aggression against it . . ." and "many vast areas remain unplowed because Cambodia does not have enough manpower to work them."