Bangkok, Thailand — Ever since talks between Peking and Moscow started, an unusual phenomenon has been taking place in Hanoi: Chinese Embassy officials have been phoning their Russian counterparts for ''warm, friendly chats'' - on phone lines they feel sure are bugged.
Outwardly the Vietnamese show no concern at these unsubtle tactics, diplomats based in Hanoi say. Peking's interest in better relations with Moscow, the Vietnamese argue, shows that China is disillusioned with the ''American card.''
Privately, however, Vietnam's friends say Hanoi is worried. Vietnam's main supporter, the Soviet Union, is after all talking to Hanoi's archenemy, China.
''Perhaps,'' an Asian diplomat said, ''the Chinese and even the Russians have already achieved most of their aims.
''They have created the image - helped by the media - that a rapprochement between their two countries is after all possible. They've forced the US to stop taking the Sino-Soviet split for granted, and they've probably improved their bargaining positions vis-a-vis Washington.''
Fallout from the talks in other Asian countries has taken mostly the form of speculation. For south and north Asian countries, tend to have a fairly wide network of international relationships, the speculation has been relaxed, almost academic.
Southeast Asian countries on both sides of the Kampuchean (Cambodian) conflict have, however, followed the talks with more interest and concern. Both sides pin a lot of hopes in the support of one or the other of the big Communist powers. Both sides could therefore be directly affected by the outcome of the talks.
Many Asians seem skeptical about China's three conditions for improving relations: that tension on the Sino-Soviet border be lessened; a solution found for Afghanistan; and the Vietnamese be pressured to pull out of Kampuchea. China's party general secretary, Hu Yaobang, has already said that progress on just one condition would be enough to get the ball rolling, and Chinese diplomats based in Asian countries are telling visitors that the key to improved relations is ''the Soviets proving that they are good neighbors.''
''I think you'll find in the long run that the Soviets and the Chinese will agree to disagree on Afghanistan and Cambodia,'' one Japanese observer remarked. ''The border condition is so much easier to solve.''
The Chinese announcement Dec. 16 that Kampuchea was the main obstacle to detente with Moscow tends to be interpreted here as a bargaining tactic rather than a reversal of Chinese priorities.
Most south Asian countries are in any case slowly moving away from heavy reliance on a single major power for their security. They are learning ''from hard experience,'' a South Asian says, that diversification in external relations is vital.
Pakistan, under Zia ul-Haq, for example, is very close to China, and is in the process of receiving a big military aid package from Peking's would-be ally, the US. But Zia still keeps up good relations with Moscow and was delighted by his 40-minute conversation with Yuri Andropov at Leonid Brezhnev's funeral.
''He was pleased not just by the flexibility he felt Andropov was showing,'' commented a diplomat, ''but by the attention Andropov was showing him.''
Zia, another observer remarked, would like a solution in Afghanistan but is also very keen to keep communications open with Moscow, whatever happens. ''His troop deployments show you what he's really worried about,'' said a South Asian diplomat. ''He has two divisions on the Afghan frontier and 17 on the Indian border.''
In the past, India and Pakistan used to hope that their friendships with the Soviet Union and China respectively, would deter attacks from the other. Today a greater deterrent might be the massive destructive power each side could unleash against the other. Last week's report of an Indian contingency plan for an air strike against Pakistani nuclear installations illustrates the new levels warfare in the subcontient have reached. ''The last Indo-Pakistani war was fought with 'elderly' tanks and first-generation jets,'' one Indian remarked. ''Now Pakistani F-16s can reach all our nuclear plants and our Bombay oil fields. . . .''
This may explain why Pakistan and India seem to be paying more attention to local detente than the Sino-Soviet talks. ''It's much more important to us - and just as hard to achieve,'' said one South Asian official.
And even India, which in 1971 signed a peace and friendship treaty with Moscow shortly before going to war with Pakistan, is now actively moving ahead with normalization talks with its old enemy, and building up relations with France and the US.
In northern Asia the Japanese seem to be taking an equally detached view of the talks. ''They're like us, you see,'' a South Asian remarked, ''they're looking for a good spread of political and economic contacts.''
Japan's relations with China are good enough for the Vietnamese and Soviets to worry about the Peking-Tokyo-Washington axis. Toyko's relations with Moscow are slightly more ambiguous.
The Soviets refuse even to talk about Tokyo's demand for the return of the Kurile Islands, occupied by the Soviets in 1945. Then there is Tokyo's concern at the Soviet military build-up north of Japan which has caused Japan to start to increase its own defense expenditures.
''The Soviets say the buildup is basically a response to US presence in the region. So, if the Sino-Soviet talks spurred the Americans and the Russians to discuss troop security more seriously, we might benefit,'' commented a Japanese official. ''But that's a long way down the road yet.''
In Southeast Asia, hopes and apprehensions are much higher. After some slight concern when the talks were announced, hard-liners seemed more reassured within the Association of Southeast Asian Nations (Singapore, Thailand, Malaysia, Indonesia, and the Philippines).
''If I were the Vietnamese, I would certainly be worried,'' Sinnahamby Rajaratnam, Singapore's deputy premier, commented. If China and the Soviets make up, said Mr. Rajaratnam, Moscow would pressure Vietnam to withdraw from Kampuchea, and the Vietnamese would be unable to refuse.
The Thais also seem optimistic. ''The key to a Cambodian settlement lies outside Cambodia,'' said a senior Thai official. ''The Chinese know there's no way to force Vietnam militarily out of Cambodia - no country can match Vietnamese stubbornness - so the only way is to talk to the Soviets.''
The Soviet Union is now virtually the only source of military economic and military aid - it runs to about $860 million a year - and Soviet officials are continuing quietly to express annoyance at Vietnam's inefficient use of assistance. The Vietnamese say there has been no reduction in the Soviet aid flow, but the Soviets seem to be providing help on a project-by-project basis, rather than working out with Hanoi a five-year aid program to coincide with Vietnam's plan.
Signs like this make some of Hanoi's opponents hope for the big breakthrough, but Hanoi has some cards of its own. They allow the Soviets access to Vietnamese bases, but they haven't allowed them to establish their own bases there.
If Moscow did ever show signs of dropping Hanoi, current speculation goes, the Vietnamese might threaten to deny them access to the important sea and land bases.