Many people have trouble dealing with teen-agers, but Alexander M. Haig Jr. has more than most. The secretary of state has recently tangled with two Nicaraguan 19-year-olds and came out, as can happen in these inter-generational encounters, badly mussed up.

The secretary summoned up his first adolescent at a House hearing on Central America. "A Nicaraguan military man," he intoned in his hard-breathing way, had been captured while directing guerrilla activities in El Salvador.

The country leaned forward. Living proof at last that the carnage in El Salvador was being fired by the Marxist fiends in Managua. That night on our television screens appeared the round, childish face of Ligdamis Anaxis Gutierrez. He was wearing a cross around his neck. He didn't seem the Cmdr. Zero type.

Blushing U.S. Embassy officials said they had no reason to believe he was anything but what he claimed to be--a student in a Mexican university who unwisely passed through El Salvador on his way home to Nicaragua.

He was, at the same time, quite resourceful. When he was picked up by the Salvadoran police, he told them he was a guerrilla with a contact in the Mexican Embassy whom he would finger. He was "snatched" inside the embassy, where he is awaiting a safe conduct so he can go back to school, and perhaps tell his classmates how he did in the secretary of state to the north.

Such is his obsession, however, that Haig picked up another teen-ager in his burnt fingers just eight days later.

Orlando Jose Tardencillas Espinosa was flown here for a singing engagement at the State Department. On paper, at least, he had star quality. He was of the same dangerous age as Gutierrez, but he wore glasses, which makes him look a little different, and he was just what Haig had been looking for: a Nicaraguan with guerrilla training in Cuba and Ethiopia.

Alas for show-and-tell, Haig's new child military prodigy said the information that had so captivated Haig was false and had been tortured out of him in the Salvadoran jail where he had been held for 14 months by treasury police, who are said to be the worst in a country of bad cops.

Tardencillas, while the lives of his State Department keepers flashed before their eyes, displayed to a select group of reporters a scar that he said resulted from an operation to remove a blood clot produced by prison beatings.

We may never hear of Gutierrez again, but Tardencillas--he's the one with the glasses--is a national hero in Nicaragua, as anyone who decks Haig is apt to be.

Now all this is hilarious and in a way heartening, since people who run foreign policy like a Marx Brothers movie may never get their act sufficiently together to do any real harm to the rest of the world.

But encounters with the jeans-and-Adidas set can be unhinging to certain explosive egos, and Haig's conduct has become alarming. From the fiasco with Tardencillas, he rebounded with more frantic moves.

In a desperate attempt to deflect Mexico's efforts to negotiate with all parties in the stew over Central America, Haig, after meeting with Mexico's foreign minister, came out rumbling about "globalizing" the conflict and calling the Soviets in to a peace parley.

The Soviets? Is not our entire effort to rid the hemisphere of their baleful presence? Did not Alexander Haig promise us last year that he would go to the "source" of arms and subversion, in Moscow, in Havana? Why was he asking the "source" to come to him?

Haig was merely trying to put the Mexicans in their place, which is a Yankee reflex, but the right wing, which was not supposed to be listening, responded with rage to the prospect of Leonid Brezhnev at the Central American peace table.

So the next day, Haig did a quarter-turn, declared that it was very nice of the Mexicans to offer their good offices, but added, lest anyone fear that something sensible might occur, that he did not think the Mexican formula would work. What he meant, of course, was that the Mexicans might fail to come up with something to ensure the overthrow of the Sandinista government, which appears to be Haig's central Latin American vision.

Nicaragua has understandably declared a state of emergency. Nicaraguans have read in the paper that they are subject to a multimillion-dollar U.S. covert activity scheme to destabilize their country. No one in the administration has bothered to deny the reports, which first appeared in The Washington Post. The other day, two bridges were blown up, and the Nicaraguans blamed the CIA. We are also, it seems, recruiting Argentinians for terrorist chores in Nicaragua. Didn't Haig tell us that his No. 1 priority was to stamp out terrorism on the globe?

Haig plainly does not know how to negotiate with teen-agers, and Nicaragua seems to have an awful lot of them. It's just one more reason to let the Mexicans do the talking in Central America.