Bangkok, Thailand — A serious outbreak of fighting along the border of Thailand and Vietnamese-occupied Kampuchea last weekend indicates that Hanoi's next dry-season offensive may not be far off.
Forecasts of such offensives have rarely been successful. But this year there is general consensus on both sides that the offensive will be larger than usual.
Sources close to the Vietnamese government say that the military wants to launch a drive against all three groups in the anti-Hanoi resistance, known as the Coalition Government of Democratic Kampuchea (CGDK). The reasons for this probably include the relatively greater aggressiveness shown by the guerrillas earlier this year, and by the approach of the 40th anniversary of the Vietnamese Army next month - something that the generals might like to celebrate with a bang. It seems probable that the offensive will be accompanied by one or more incursions into Thai territory.
In the past, Vietnam's Foreign Ministry is known to have opposed large offensives and incursions, arguing that these only tighten the deadlock between Vietnam and its pro-Western neighbors. It would not be surprising if the Foreign Ministry took the same line this year. The military, however, usually prevails in such high-level debates.
This weekend's fighting concentrated on the border camp of Nong Chan, controlled by the Khmer People's National Liberation Front (KPNLF), the larger of the two noncommunist members of Kampuchea's resistance coalition. The camp has already been overrun by Vietnam once, in early 1983.
In theory the monsoon rains, which usually begin around May and end in October, favor the lightly armed guerrillas. But the guerrillas do not seem to have been very active during the past rainy season. This is attributed here partly to a departure by Vietnam from its ''season'' pattern. With the onset of the rains they usually pull a large part of their forces off the border. This year they did not do so, and a blocking screen of Vietnamese and Kampuchean Army forces opposite the main guerrilla camps is thought to have inhibited guerrilla penetration into Kampuchea (formerly Cambodia).
During the rains, however, the Kampuchean guerrilla forces - numbering around 50,000 but at best loosely coordinated - have been resupplied by their respective allies. The KPNLF has received small arms from the Association of Southeast Asian Nations, and antitank and antiaircraft weapons from China. The Khmer Rouge, the communist member of Kampuchea's opposition coalition, has reportedly received an unspecified number of 85mm artillery guns from China.
But though the coalition forces are better equipped, they are no more united. The attack on Nong Chan came at a time when the leadership of the KPNLF is reportedly split.