Economist Arthur B. Laffer usually gets $4,000 per talk when he speaks for money. But yesterday he stood up for free with his idea of America's biggest problem: government incentives for the wrong things.

He joined dozens of oratorial headliners performing gratis this week in a sort of marathon Chautauqua program. Dr. Henry J. Heimlich spoke on his medical maneuver to save choking diners. Helga Sandburg treated the crowd to reminiscences of her father Carl. and William Meredith, poetry consultant to the Library of Congress, warned that "Tests have proven that the average person in this room is getting less than the required human minimum of poetry."

It wasn't a three-ring circus only because there were more than three rings, all under the broad aegis of the International Platform Association's five-day 148th annual convention at the Hyatt Regency, with participants ranging from Abigail Van Buren (Dear Abby) to Zbigniew Brzezinski.

Between now and sometime in the small hours of Saturday morning, approximately 1,000 IPA members at the convention will be eyeing one another speculatively: the speakers showing their wares like merchants at a bazaar; the program directors who hire speakers weighing a medical researcher against a comedian, an economist, perhhaps even a folksinger or a magician as a drawing card for his convention, banquet or annual gala. Besides the speeches - given at a rate of more than one an hour during the day - each evening concludes with a variety show that can include jugglers, dancers or almost anything.

"The program chairmen are looking for blue-ribbon talent on the hoof,' and there won't be much of it," said Warren Knox, a program chairman and speaker from Cleveland.

One talent scout on the scene was Dr. Everrett Peterson, in his 22nd year as president of the 300-member Denver Exeuctive Club. "I get them through the newspapers, television and here," he said. "I have a budget of $30,000 to $35,000 per year to spend on speakers." His next will be Harry Reasoner, who costs $5,000, and he recently turned down an offered from Jerry Ford.

"Ford's manager called me and offered him for a fee of $13,000 plus $4,000 expenses for his Lear jet and four bodyguards," Peterson recalled. "I wouldn't think of having him - that's too much to pay for the name."

It's that kind of business. In the foyer outside the grand ballroom, speakers and buyers in the words-to-riches trade mingle and hustle among the display booths, exchanging business cards and telling stories of life on the stand-up circuit.

On the first full day of the convention, the program directors present did not seem sold on any of the talent shown. But making a hit at the IPA convention can mean smashing, nationwide success.

Yesterday people remembered the story of Carl Stokes. When his term as mayor of Cleveland was nearing its end, Stokes came to the IPA convention, gave a speech and within the next three weeks received bookings for $150,000 worth of talks. NBC, which was covering the convention, was so impressed that it offered him an anchor position on a news show, provided he would drop the $150,000 in engagements. Stokes thought it over for a while and accepted.

Howard Jarvis, the instigator of Proposition 13 in California, gets $3,000 per lecture. "When Jarvis spoke at our club," recalled a program director, "we ha a baritone singing 'The Impossible Dream' and the tears just started rolling down Jarvis's face. He couldn't speak for quite a while. He told us that he had cried because what he had done was impossible, but he did it."

Henry Saint Laurent is from Quebec and one of the talks he offers for sale is entitled "Quebec vs. Canada." Resplendent in red trousers and blue jacket, he stands in the foyer, nervous and vivacious, shifting from foot to foot, his voice rising and falling enthusiastically as he talks about the life of a traveling public speaker:

"It's living in a suitcase and spending a lot of time in airports and always having somebody who wants to show you the historic sights about which you could care less. You have to be callous in this business. You're a hero when you arrive and after you speak, you're on your own. Speaking is show-business. The performance and the applause are the satisfaction."

Public speaking has come a long way since Daniel Webster formed the American Lyceum Association, prede- cessor of the International Platform Association, and Ralph Waldo Emerson gave the first public address in this country for which a fee was recorded: $5 plus oats for his horse.

"They made a lot of trouble about the oats," says Dan Moore, board chairman of the IPA. "It seems there was an oat shortage at that time - something like our gas shortage - but he impressed them so much that they finally gave him the oats."

Within six years after Webster founded his first Lyceum, there were 3,000 of them in American communities along the east coast and as far west as Ohio. They were succeeded by the Chautauqua movement, traveling shows that combined a circus atmosphere (including giant tents, and sideshows) with cultural content. In this century, Chautauqua folded its tents, dealt three strikes by the competing attractions of movies, the automobile and radio, and what was left was a speakers' circuit.

When television came in strong, Moore recalled, "everyone thought television would kill the lecture business, but just the opposite happened. Television whetted the appetites and the airplane made it possible for anyone to moonlight as a public speaker all over. When President William Howard Taft was a member of our organization, he said he made more money on speaker's fees than he got in his presidential salary. But it would take him 11 days to go to California by train, give a talk and come home again. Today, you can give a talk in California and get a night's sleep in your own bed in Washington."

Laffer yesterday received the 1979 Daniel Webster Award, given for the most influential words spoken on our nation's most important problem. His estimated $120,000 per year in about 30 speaking engagements is comfortable but not outstanding in the public speaking industry, whose annual gross revenues are in the hundreds of millions of dollars.

Another award was collected by Isaac Asimov, who also collects up to $10,000 per lecture and gives about 200 per year - in spite of a phobia (odd for a science fiction writer) that keeps him off airplanes. Bob Hope gets $30,000 per appearance, Gen. Alexander Haig gets $15,000, and Henry Kissinger ranges from $10,000 to $25,000, probably averaging around $15,000. Lowell Thomas, 87, president of the IPA, limits himself to four talks per year - $40,000 worth.

Some of those in the lower tax brackets filled the "Hal Holbrook Showcase," a daily convention attraction named after the man whose impersonations of Mark Twain made the one-man show a national institution. The six speakers at the first day's showcase gave brief samples on subjects that included China, Iran, the Olympic games and stress management.

"The minute I sat down after my speech," recalled one speaker, "a man handed me his card. He's a gynecologist, for god's sake, but maybe he has some university speech in mind, and I do colleges like Jane Fonda. We have the same agent."

During the showcase, each hopeful speaker, identified by a namecard on an easel, goes on stage and does his stint, while the audience looks attenitive but not particularly stimulated. The mood is like a tryout for a Broadway show, with 1,000 producers in the audience. Everyone is handed an evaluation card on the way in; report cards are filled in ranging from "poor" to "excellent" and the sheets are handed in and tabulated.

Before going on, the hopefuls are given a group pep-talk and briefing by a specialist in selling yourself as a public speaker:

"Always have a resume - double-spaced with large type - and an abundance of colorful flyers and name cards. If there are professional associations in your field, join them - you never know when you'll get a job or make a contact. Send out lots of press releases."

Even at the low end, the fees for one or two talks would have kept Ralph Waldo Emerson solvent for a year and his friend Thoreau too rich to be comfortable. But the oratorical techniques have not kept pace with the inflation of fees, according to Dan Moore:

"Henry Ward Beecher was the first public speaker to get $1,000 for a speech, but he earned it. He was an abolitionist, and once he talked in Richmond to a crowd that had the ropes in its hands to lynch him. After an hour, they gave him a standing ovation with the rope still in their hands. Youdon't get speakers like that any more - they slouch all over the podium and people come to hear them because they are powerful or well-known.

"Daniel Webster would have been ashamed." CAPTION: Picture 1, Clockwise, from top left, Helga Sandburg, Isaac Asimov, Bob Hope, Gen. Alexander Haig, Henry Kissinger, William Meredith, Lowell Thomas, Henry J. Heimlich, Arthur B. Laffer and Abigail Van Buren, center. Picture 2, Reviving a choke victim: Dr. Henry J. Heimlich the lecturer, and Sarah Tinsley and Dan Moore the demonstrators. Millie Deutsch of International Platform Association at right; by Larry Morris - The Washington Post.