The conventional wisdom about Third World debt is that the crisis is over and future problems are "manageable." But there are some warning signals that this may be too reassuring an appraisal.

What John H. Makin of the American Enterprise Institute calls a "remission" of the problem applies only to the "Big Four" Latin American debtors -- Mexico, Venezuela, Brazil and, one hopes, Argentina.

In any event, to speak of a "global" Third World debt problem is misleading. The problems vary widely. Thus, the Philippines is on the verge of economic collapse with a credit rating next to zero and a $26 billion debt.

Another disaster area is sub-Saharan Africa, which won't have the money to pay back $2 billion of IMF loans in the next couple of years.

And in Latin America, once you get past the Big Four, it's altogether a different ball game. As development aid expert Christine A. Bogdanowicz-Bindert points out, smaller countries such as Bolivia, Peru and Nicaragua for all practical purposes have already defaulted on their debt, and others, such as Chile, Jamaica and the Dominican Republic, are wracked by political and social turmoil.

As she goes on to say in a study for the Overseas Development Council, these problems have been ignored by American commercial banks, in part because they have bigger fish to fry, such as trying to protect their investments in the Big Four. Also, smaller debtors are not regarded by bankers as as big a threat to the banking system or to the health of the American economy.

Meanwhile, the relatively better outlook in the Big Four is fragile. In part, the 1984 improvement can be traced to a sharp cut in their imports (at the behest of the International Monetary Fund) and a strong American economy that sucked in their exports. That situation is changing; U.S. economic expansion has slowed, and Third World exports are again slipping.

Another straw in the wind is the unchallenged fact that the "success" stories, such as Mexico, have been built on their ability to reduce balance-of-payments debts. But they have been notoriously deficient in improving their domestic economies. Necessary economic growth has been halted. (Mexico, of course, will have added troubles as a result of sliding international oil prices.)

IMF Managing Director Jacques de Larosiere likes to point out that, overall, the aggregate balance-of-payments deficits of Third World countries have been shaved from about $110 billion a year in the early 1980s to less than $40 billion last year.

That shows, he says, how successful have been the "adjustment programs" required by the IMF -- a euphemism for belt-tightening and fiscal reform. There is no doubt that this is a spectacular result, but it has been achieved mostly at the expense of the local standard of living. The Bank for International Settlements at Basle noted in its recent annual report, "They now need to bring domestic inflation under control, and to restore domestic interest rates to levels that are positive in real terms."

That will take some considerable skill by everyone involved in rescheduling the big pileup of maturing loans in the next five years. It will also take a major reversal of the protectionist trend among the industrial nations that blocks poor countries' exports.

At a recent international monetary conference in Hong Kong, former New York Federal Reserve Bank president Anthony Solomon warned that "the best that can be realistically hoped for in the heavily indebted countries of Latin America and elsewhere is a mitigation of current restrictions, controls and inefficiencies."

A realistic possibility, Solomon said, would be some export growth -- perhaps on the order of 3 percent to 4 percent -- which would be enough to help Third World nations pay the interest on their debt, but not enough for them to reduce their real debt burden, either in relation to GNP or to foreign exchange earnings.

But this would be better than what Solomon labeled a "populist alternative": an attempt to pump up developing economies with big government spending programs accompanied by an extension of trade controls.

Henry Kissinger has suggested a new development institution that would borrow money in world capital markets for relending to Latin American countries at low rates. The financial establishment is always dubious about new ideas, but a reexamination of the multi-faceted debt problems is clearly in the United States' self-interest.

For example, Roger A. Sedjo of Resources for the Future has pointed out that to stave off major default, the United States will have to let debtor countries run trade surpluses indefinitely. That's the only way they can service their debt. But continuing Third World surpluses requires a steady run of U.S. trade deficits.

Meanwhile, there is the question about what should or can be done about the IMF austerity demands, especially the fund's insistence on basic reforms in a very short time span.

The charge that the IMF is recklessly austere angers de Larosiere. His response is that the real trouble is not the IMF loan conditions, but the economic excesses that got many of these countries into trouble in the first place.

But hostility in the Third World to the IMF is a fact of life, and it will have to be dealt with. An internationally respected central banker thinks that the IMF could show more flexibility and should get away from the fixed formula it seems to apply to every country. He says:

"Because they are an international institution, the pressure in their executive board is that what's good for country A is good for country B. The IMF has a little cookie cutter that they apply to every country -- okay, you've got to devalue, you've got to restrain the money supply, you've got to reduce the deficit, and so on. They go by the book."