Asia's underdeveloped nations, staggering under oil price hikes, huge foreign debts and overpopulation, have been enjoying an economic respite through improved sales and prices of their homegrown timber, tin, sugar and rubber.

But the prevailing sense of well-being and people of recovery may fade fast if initially promising efforts at controlling birth rates and reducing dependency on oil do not succeed. The signs of recovery seem in some ways to have even dampened the once-intense interest in moving away from petroleum-dependent economies.

Many of these nations are now mortgaged to the hilt. The Philippines, Indonesia, India, and Pakistan all have debt service ratios approaching 20 per cent. By and large, they lack the kind of industrial base that could withstand sudden recession and must rely on the Western economies that buy their raw goods and keep them afloat.

Few of the small, less developed nations here enjoyed much financial health before 1973, but the quadrupling of oil prices since then has made matters considerably worse. The spiral has undercut whatever improvements in living standards a cut in births rates may have secured. Those nations that have moved the most swiftly to deal with the energy crisis seem also to have had the most success in solving the key social and political problem of raising real incomes and access to consumer goods.

The mini-economies - Singapore with a per capita gross national product of about $2,700, and Hong Kong with $2,100 - are doing well, as befits the vital role they have carved out refining oil, lending money and manufacturing.

Of the larger economies, the most active in energy development seem to be the most isolated politically. Taiwan, in particular, moved by the ongoing Peking campaign to cut off its trade and diplomatic ties with the rest of the world, has begun to construct a series of nuclear plants that are expected to provide nearly half of the island's electrical power needs.

South Korea, with similar problems of political isolation, is also moving fast to build nuclear plants. But in much of the rest of Asia, interest in the nuclear alternative to oil has waned as nuclear safety fears mount and the price of construction and nuclear fuel increases.

After the panicky months of late 1973, most states have found they can live with the higher oil prices, even if they face some vague, future financial crunch as their payments' balances continue in the red.

"They have found that the supply of oil did not become an impossibility," said Adrian Fioretti, manager of international marketing analysis for General Electric, which has been peddling nuclear plants in this are. "In the last 48 to 24 months they have backed off considerably (in nuclear purchases) . . .If they were planning on two plants now they say, well, go ahead with just one."

In the Philippines, where dependence on Mideast oil and low living standards are relatively serious, a $1.2 billion, 620-megawatt nuclear plant is under construction, but plans for construction of 11 additional plants are no longer mentioned. The estimated construction costs of such plants have doubled since the early 1970s, and the cost of the uranium ore for the nuclear fuel also has skyrocketed.

Asian nations seeking to develop a non-aligned political stance, which to a certain extent includes the Philippines, also wonder if they really gain much by lowering dependence on the Middle East only to have to rely on the world's few uranium exporters - such as the United States, Canada, Australia and South Africa.

Located along the volcano helt, Asians nations like Indonesia and the Philippines could produce considerable cheap energy through geothermal plants, powered by the steam from natural underground heat sources. But in many instances, Floretti said, "These are small quantities of power and they often aren't located next to large cities."

Although few Asians have starved this year, the amount of meat and eggs people are getting is still low. Indonesians and Filipinos are getting no more than 45 grams of protein a day, about half of what Australians eat or two-thirds of what Taiwanese and Koreans are getting. And, according to one official of the Philippine Agriculture Department, "Protein intake among most Filipinos has declined, or at least not improved."

Income differences in Taiwan, where per capita GNP is now about $1,000, have been reduced through growing light industry jobs and a stringent government policy against corruption and high-living among top officials. In nations like Indonesia such restricrions are much less effective.

The natural market forces brought what price improvements the underdeveloped sellers here have enjoyed, fairly substantial in rubber and timber, less encouraging but somewhat better than 1976 in sugar. Asian nations concerned have all tried to cut births through mass information campaigns, which seem to have had an effects as young Asians realized what large families were doing totheir pocketbooks.