Hanoi's push against Khmer rebels

Fighting on the Thai-Kampuchean border has finally subsided, but confusion remains both about the extent of the offensive and the Vietnamese intent in launching it.

Hanoi's gains are clear: in less than a week they have destroyed two important bases of the anti-Vietnamese Coalition Government of Democratic Kampuchea (CGDK). The Khmer Rouge have lost Phnom Chat, which had about 3,000 guerrillas and some 30,000 civilians. Prince Sihanouk has lost his headquarters at the grandly named Sihanoukville, which housed around 30,000 peasants and perhaps 1,500 guerrillas - whose fighting abilities were not, however, highly regarded.

Overall, Hanoi seems determined to push the coalition off Cambodian soil, thus embarrassing the Association of Southeast Asian Nations (ASEAN) and destroying any territorial claims that the coalition has to legitimacy.

The Vietnamese operations this year seem to be a combination of old and new tactics. They launched a similar drive at the end of the dry season last year, and reportedly succeeded in cutting Khmer Rouge supply lines south of the main stronghold of Phnom Melai.

In recent weeks Hanoi has claimed that the Chinese were increasing arms shipments to the anti-Vietnamese coalition in preparation for the rainy season, when Hanoi's conventional forces supposedly find themselves at a disadvantage. Ironically, one of the CGDK leaders, Mr. Son Sann, provided confirmation of this claim on the day the Vietnamese launched their attacks. Speaking in Kuala Lumpur , the Khmer leader told reporters that his group would ''be receiving something from China very soon.''

This year's attacks will further hamper the coalition's already limited ability to harass the Vietnamese-supported government in Phnom Penh. It will probably ensure that the first of the regular troop withdrawals that Hanoi announced last month will take place on schedule. Last year Hanoi announced a troop withdrawal in June.

And by removing Prince Sihanouk's toehold on Kampuchean soil, Hanoi may be hoping to make the prince think again about his participation in the coalition. His enthusiasm for it has never been great, but his reaction to the loss of Sihanoukville has been strangely muted. Reports today, some five days after the loss of the base, say that the prince has simply expressed his concern at the reverse, and has promised to visit his compatriots shortly.

The most recent fighting comes exactly two months after Vietnamese troops captured and razed the Son Sann camp of Nong Chan. The Khmer Rouge still have their main stronghold of Phnom Melai, but Son Sann's other camps are desperately vulnerable. One, Nong Samet, probably has about 100,000 refugees in it. Another, Ban Sangae, has long been considered strategically indefensible by Western military analysts.

In the short run the fighting will reinforce ASEAN solidarity, which was slightly shaken at the recent foreign ministers' meeting where some members showed interest in a Vietnamese proposal for regional dialogue. In the long term , however, ASEAN will have to decide whether to rebuild the coalition from the ground up, or look for another solution.

Hanoi revealed what it had in mind late on April 7. The Voice of Vietnam radio carried a commentary from the official Khmer press agency. The commentary once again castigated ASEAN, Washington, and Peking for their support of the coalition, and called for negotiations as the ''only way'' to solve the Kampuchea question.

The extent of the fighting is harder to gauge. Foreign journalists have been unable to go to the border. Partial reports suggest that so far some 50,000 refugees have been forced into Thailand, up to 200 killed and more wounded. Khmer resistance losses have not been announced, but a diplomat from one of the countries actively supporting the coalition described losses as ''heavy.''

Thai military sources describe the fighting as the most serious border incident since the Vietnamese overthrow of Pol Pot in 1979. But they seem to be forgetting the Vietnamese incursion of June 1980, when at least 18 Thai troops were killed in a single battle, and when two Thai aircraft were shot down. Five Thai soldiers have been killed in this week's fighting, and no aircraft lost.

Bangkok's allies have expressed their concern but do not seem too upset. A source conversant with Peking's point of view described the border clashes as ''not very serious.'' While the Thais have estimated that up to 6,000 Vietnamese troops were involved, this source suggested the actual figure was closer to 2, 000.

Speaking to reporters in Bangkok today, Assistant Secretary of State Paul Wolfowitz said that the US would expedite military supplies destined for Thailand. He was, however, unable to give a clear idea of the border fighting, even though he had visited the area Wednesday.

The Thai Army officers who are stressing the gravity of the current fighting may well have the April 18 general election in mind. One of the key electoral issues is the political role of the military: late last month senior officers narrowly failed to stop changes in the constitution limiting the military's role in government. Many observers here believe, however, that the Army has not yet given up the fight. ''They are emphasizing the border fighting,'' one prominent opponent of the military suggests, ''to remind the people of the indispensability of the armed forces.'' Another goes further: ''The situation is very threatening. Internal ferment and problems on the border are the traditional signs of a coup.''