Two months after the Vietnamese Army's brief strike into Thailand artillery and small-arms fire continues to be heard almost daily along the Thai-Cambodian border. The clashes have helped give rise to speculation in Bangkok that Hanoi is planning to cross the frontier again.

Such talk has been fueled by reported troop movements, a new, harsh tone to denunciations from the opposing capitals and the apparent breakdown of diplomatic efforts to soften the current mood of confrontation.

However, many analysts caution that nothing may happen at all. They cite Thai and Western intelligence agencies, with a spotty record of anticipating Vietnamese moves, as well as a possible distortion of information to discredit Hanoi.

Moreover, at the coming United Nations General Assembly session, Vietnam hopes its client government, headed by Heng Samrin, will finally unseat the Khmer Rouge delegation still recognized as Cambodia's official representative. Bloody border fighting with heavy civilian casualities would not win votes for Heng Samrin from undecided nations.

Any cross-border attack would be seen as a warning to Thailand to stop supporting Khmer Rouge and rightwing Khmer Serei guerrillas in their fight against the estimated 200,000 troops Hanoi has deployed in Cambodia.

Earlier this month, Western intelligence sources said two more Vietnamese divisions had appeared in Battambang, the Cambodian province from which Hanoi's brief incursion into Thailand in June was launched in a bid to wipe out guerrilla forces based along the Thai-Cambodian border.

Thai border forces, meanwhile, have reported firing on at least five Vietnamese patrols which were conducting nighttime reconnaissance missions inside Thai territory this month.

Vietnam and its client government in Phnom Penh blame the rising tension on Thailand, which they say is acting on behalf of China and the United States. Thailand continues to recognize and, many diplomats believe, to arm the deposed Khmer Rouge government of Pol Pot.

Radio Phom Penh said many Thai provocations had occurred in the Phnom Malai Hills, south of the Thai town of Aranyaprathet. Shortly after the June incursion, Vietnamese commanders turned their attention to Khmer Rouge positions there, launching artillery and ground attacks that are still in progress.

Battlefield developments like these appear to take on a new significance in light of the apparent impasse in diplomatic efforts to find a compromise.

Vietnam, Laos and the Phnom Penh government have stood by proposals their foreign ministers announced after a meeting in the Loatian capital of Vientiane in July.

Their plan centered on creation of a demilitarized zone along the Thai-Cambodia border. It also called for nonaggression pacts and removal of anti-Vietnamese guerrillas from refugee settlements.

The Vientiane plan was rejected by Thailand and the four other members of the Western-oriented Association of Southeast Asian Nations. Meeting two weeks later, ASEAN representatives proposed instead U.N.-supervised demilitarized zones, located wholly within Cambodia, to provide a place of refuge for civilians.

Thailand could not allow any demilitarized zone on its own territory, it said, because it is not at war with Cambodia and is neutral in the conflict within the country.