PRESIDENT REAGAN has made another of those remarks about the poor that put the let's-have-a-flap industry into high gear all over town. At a question-and-answer session for high school students, Mr. Reagan said "our programs of social aid to our own people are such that where there is hunger . . . you have to determine that that is probably because of a lack of knowledge on the part of the people as to what things are available. Not only is the government doing much in that line, but there has been about a three times increase in private charity. . . . And between those two sectors, I don't believe that there is anyone that is going hungry in America simply by reason of denial or lack of ability to feed them. It is by people not knowing where or how to get this help."

The outcry was swift and predictably overstated. If the president distorted the full nature of the hunger problem, the critics distorted the distortion. "The president announced today that hunger in this country is caused by ignorance," Sen. Edward Kennedy said, and suggested that administration policies were the greater cause. Try it this way:

1. The president is right in saying that part of the hunger or poverty problem is that people don't know "what things are available." The purest of federal welfare programs and largest other than Medicaid is food stamps. For other forms of aid you have to be old or blind or disabled or have dependent children; for stamps all you have to be is poor. Only about two-thirds of the people eligible for stamps are in the program. Millions don't sign up -- particularly elderly eligibles and members of the working poor. A survey some years ago showed that ignorance of the rules was a major cause. (And yes, as part of the budget cuts of 1981 the administration killed an "outreach" program meant to help dispel that ignorance.)

2. The president is wrong in suggesting that ignorance of the rules is all there is to it. Far from it. More than three years into the recovery from the last recession, the unemployment rate is still over 7 percent, the percentage of the unemployed who lack unemployment insurance is at a record high, a seventh of the population lives below the poverty line, the poverty rate for children is 21 percent, the share of all income going to the richest fifth is up, the share to the poorest fifth is down. A lot of people are hurting. The president glides by that.

3. Although this administration's budget cuts and economic policies have exacerbated these problems, the causes are deeper and predate the Reagan years. For instance, basic welfare benefits through Aid to Families with Dependent Children have lost a third of their purchasing power to inflation over the past 15 years (even as female-headed families have come to account for a greater share of the poor). In fact, it was only last year that the value of these benefits finally ticked up again -- because inflation declined. Increasingly, economists who deal in such matters have also begun to worry about a fundamental wage erosion in the lower and middle reaches of the economy, the result in part of foreign competition but, they suspect, of much else as well. There are other such broad trends -- the extent to which housing costs have outstripped incomes in recent years, for example -- against which existing government programs are only palliatives. President Reagan isn't thinking about these issues. Neither are most other current political figures, in either party. That is what the debate should be about, and not the president's unfortunate off-the-cuff remark.