The long-contested Cambodian jungles may see fighting with a different twist: noncommunist Southeast Asia joining China to arm Cambodian insurgents in an effort to force occupying forces back to Vietnam.
The issue of whether to funnel arms to a new coalition of communist and noncommunist insurgents in Cambodia (Kampuchea) will be up for discussion this weekend by foreign ministers of five Southeast Asian countries.
So far the main flow of outside arms to fight Vietnam has gone from China to the Khmer Rouge - the communist rulers of Cambodia from 1975 to 1979 - with the indirect cooperation of Thailand. Only a small amount of Chinese aid has gone to non-communist.
Now the prospect of a ''loose coalition'' between noncommunist insurgents and the UN-recognized Khmer Rouge gives noncom-munist Southeast Asia a legal way to ship arms to noncommunists.
The conference of the Association of Southeast Asian Nations (ASEAN) at Pattaya, Thailand, thus has important implications for the future both of communist Indochina and the noncommunist group, which consists of Thailand, Malaysia, Singapore, Indonesia, and the Philippines.
The conference already has backed a Singapore proposal to form a loose ''united front'' between communist and noncommunist resistance groups fighting some 200,000 Vietnamese troops in Cambodia.
The ASEAN group faces other issues, too:
* Should ASEAN nations jointly urge China to prod its Khmer Rouge ''client'' to accept the Singapore proposal? The proposal has been accepted in principle by the noncommunist forces of Prince Sihanouk, former ruler of Cambodia, and Son Sann, Sihanouk's onetime prime minister.
The conference itself urged the Khmer Rouge to accept the idea, and Khmer Rouge has asked for two months to consider it.
* If arms are supplied, should they go to resistance at an early point, or should delivery await concrete evidence of unity and growth by the ''united front''?
Hanging over this is the need to paper over a potential split between Indonesia and the other ASEAN members, especially Singapore, Malaysia, and to some extent Thailand.
Indonesia Foreign Minister Mochtar Kusumaatmaja has warned against ASEAN's supplying arms in Cambodia. He says such an action would abandon the principle of ASEAN support for a political solution.
Singapore's proposal, made last month, calls for a ''loose'' coalition between Khmer Rouge (with about 35,000 fighters), Son Sann (about 9,000 fighters), and Sihanouk forces (still smaller). Cooperation theoretically would be easier because there would be no need for detailed negotiation on the sort of government Cambodia would have if the ''united front'' wins power.
ASEAN nations have long favored support for a resistance group not so closely associated with China and free of the reputation for atrocities during Khmer Rouge rule.
But the prospect of an insurgent coalition has created a rift between Dr. Mochtar and other ASEAN leaders. If authoritative, Dr. Mochtar's statements show a difference with Malaysia (which has recently come out in favor of arming noncommunist Cambodian insurgents), as well as with anti-Vietnam ''hawks'' like Singapore and Thailand.