Hanoi lights a candle at the end of the Kampuchean tunnel

In a diplomatic initiative prior to important meetings in Tokyo and New York next month, Vietnamese Foreign Minister Nguyen Co Thach has indicated his country's willingness to consider neutral mediation in the five-year dispute over Kampuchea (Cambodia).

Japan's Kyodo News Service quoted Mr. Thach as opening up the prospect of ''an international supervisory commission of neutral nations to play the role of peacekeeping in Kampuchea.'' He cited the example of the 1954 Geneva and 1973 Paris agreements ending the first and second Indochinese wars.

Kyodo said the foreign minister made the remark in an interview with its correspondent in Hanoi Tuesday. A spokesman for the Vietnamese Embassy in Tokyo confirmed the Vietnamese position.

Japanese Foreign Ministry officials were closely studying the text of the interview. They said it seemed to represent a significant move forward by Vietnam, which had previously rejected any mediation by the United Nations and had been reluctant to accept any sort of international monitoring team in Kampuchea.

The timing of the statement is considered significant, as Thach is visiting Tokyo Oct. 1 to 4 for talks on the Indochina situation with his Japanese counterpart, Shintaro Abe, and other officials.

The meeting with Abe marks the first formal ministerial contact between Japan and Vietnam in six years. Relations have largely been in limbo since Vietnam moved into Kampuchea in 1979 to support the present regime of Heng Samrin.

After his Tokyo meetings, Thach is scheduled to go to New York to attend the UN General Assembly. The UN continues to recognize the tripartite Coalition Government of Democratic Kampuchea (CGDK), headed by Prince Norodom Sihanouk, as the representatives in the world body. The largest element of the CGDK is composed of Khmer Rouge troops, which is commanded by the ousted Cambodian leader, Pol Pot.

Kyodo quoted the foreign minister as saying that Vietnam was ready to discuss unconditionally proposals on Kampuchea put forward by the six countries in the Association of Southeast Asian Nations (ASEAN - Thailand, Indonesia, Singapore, Malaysia, Brunei, and the Philippines) and by the three Indochinese nations (Vietnam, Kampuchea, and Laos).

Australia recently proposed that the two sides hold exploratory talks without preconditions in Canberra. In Singapore, former Thai Prime Minister Kriangsak Chamanan, said Wednesday that ASEAN had dropped a demand for an unconditional Vietnamese troop withdrawal from Kampuchea prior to peace talks. Kriangsak, who visited Hanoi recently, said Vietnam wanted a dialogue with ASEAN focusing on broad regional issues, while the noncommunist Southeast Asian grouping wanted to confine initial talks to the Kampuchea issue.

(However, Hanoi indicates its security can only be guaranteed by having a pro-Hanoi government in Phnom Pehn. For ASEAN, the issue is having a neutral government in Kampuchea.)

Japan has repeatedly offered to provide aid for the rehabilitation of Indochina in return for the phased withdrawal of the 160,000 to 180,000 Vietnamese troops estimated to be in Kampuchea. It has also offered to use its close ties with ASEAN to get talks under way.

Responding to this, Foreign Minister Thach said Vietnam welcomed Japan's possible mediation if it acted on a neutral footing and not by siding with ASEAN or China, which support the CGDK.

He said his previous reluctance to go to Tokyo was because Japan appeared to have tried to damage the honor of Vietnam by applying political pressure through such means as the suspension of economic aid (after the 1979 intervention).

Japanese officials said Thach and Abe would discuss possible resumption of aid.