Tek Kor's days as Thailand's one-man population explosion are not over yet.

The 41-year-old meatball vendor and father of 22 arrived here today to undergo a much-publicized operation at a free "vasectomy festival" organized by Thailand's leading family planning campaigner. But he changed his mind at the last minute, claimed he had been tricked into believing he would be paid 1 million baht (about $37,000) and drove off with six of his seven wives with a vow to marry his eighth wife soon and produce still more children.

Meechai Viravaidya, the organizer of the free vasectomy clinic timed to coincide with American Independence Day, had hoped that the conversion of Thailand's "family planning enemy number one" would help dispel fears among many Thai men that a vasectomy would result in sexual impotence. But he denied having offered any money to Tek Kor and said he had no idea where the meatball vendor got the impression he would be paid.

Before Tek Kor withdrew, there had been concerted efforts by local and U.S. "prolife" groups to sabotage what they called Meechai's "depopulation program."

Tek Kor, whose real name is Saisupat Terrapabsakulwong, is from Nakhon Pathom, about 20 miles west of Bangkok, and he is also known as the Nakhon Pathom Casanova. He said he had been influenced by letters and cables sent to him by the U.S.-based Club of Life and other anti-birth control organizations urging him to renege on his earlier pledge to have a vasectomy on July 4.

A June 23 letter from the Club of Life, which claims 50,000 members in 40 countries, expressed "deep concern" that Tek Kor would become a "tool" for Meechai's "genocidal" and "treasonous" family planning program.

Tek Kor seemed to echo some of the group's arguments when he declared before leaving the vasectomy clinic set up in a ballroom of a luxury hotel here, "I think ambitious, hard-working people like me should be encouraged to have lots of children to help build the nation."

He also said, "Vasectomies are meant for those who are lazy, poor and unable to afford more children." But, he added, "I am better off and able to afford many more children."

But before today's change of heart, Tek Kor had said publicly that he wanted a vasectomy because it was cheaper and safer than providing his wives with contraceptives and that he could not afford any more additions to his family.

Although technically illegal, polygamy is tolerated in Thailand under a system in which some men take "minor wives." Only the first wife is officially recognized, but the minor wives are often socially accepted, and the children have legal status.

Tek Kor, a pudgy man of Chinese origin, married his first wife, Siem-ung, when he was 21 years old and his seventh about two years ago. Siem-ung said she was "furious" when a month after marrying Tek Kor, he took a second wife. But she learned to live with the situation and "had no emotional problems when he married the third, fourth, fifth, sixth and seventh wives."

Tek Kor, who says he sleeps with his wives in a rotation system according to their seniority, now plans to marry a farmer's daughter from northern Thailand, he said today. He said he met her eight years ago when he married his fifth wife, Somboon, who also introduced him to number six and seven.

Tek Kor said he needed many children to help him with his meatball business, but he has rejected suggestions that having a large family is merely a clever way of obtaining cheap labor. Regardless, Tek Kor tirelessly promotes his pork meatballs -- he arrived at today's vasectomy festival in a battered pickup truck with a billboard advertising them -- and he credits his special meatball recipe for his sexual prowess.

Meechai, the family planning advocate known as Thailand's "condom king," has never been one to pass up a gimmick either. At today's vasectomy festival, his private, nonprofit Population and Community Development Association offered various fund-raising items for sale, including T-shirts emblazoned with slogans such as, "A condom a day keeps the doctor away."

Also available were T-shirts depicting Winston Churchill flashing his famous "V" for victory sign above the slogan, "Stop at Two."

Meechai, who also seems fond of symbolism, served free hot dogs and meatballs to today's recipients of vasectomies. He said July 4 was chosen as "a way of thanking the United States for its assistance in family planning." The Thai program now receives about $150,000 a year in U.S. aid, he said.

Three other mass vasectomy festivals are held annually: one on the birthday of the king of Thailand, and the others on Mothers' Day and Labor Day. Last December on the king's birthday, Meechai claimed a world record for mass vasectomies when 45 doctors performed 1,197.

Today, four doctors planned to perform 80 to 100 free vasectomies on volunteers who came to the new Imperial Hotel across the street from the U.S. ambassador's residence.

Among the patients was the hotel's managing director, who said that from now on, he was offering rooms for half price to any guests who had had vasectomies. But he acknowledged that the hotel would have to take guests at their word.