Thailand-The creep who confessed to killing JonBenet Ramsey had another bizarre secret up his sleeve in the months before his arrest – he was visiting a surgical center that specializes in sex-change operations.

Staff at the Pratunam Clinic, Thailand’s top transgender center, told the Daily News yesterday that 41-year-old John Mark Karr was a patient of theirs – but wouldn’t say how close he was to getting “sexual reassignment” surgery.

“Yes, he had treatment here,” a representative said. “He was our patient. He came a number of times. But we cannot give out details on his treatment as we are ethically bound to keep these things private.”

The disclosure came a day after The News reported that Karr sought cosmetic surgeons’ help changing his face in the anything-goes sex bazaars of Bangkok. In his nine months there, he made just 12 phone calls from his seedy hotel room – nine of them to plastic surgeons.

Two calls were to the Pratunam Clinic, which specializes in putting men under the knife to become “ladyboys” and also sponsors the annual World’s Most Beautiful Transsexual competition. It charges $1,600 for the surgery, which could cost $25,000 in the West. Karr was nabbed in Bangkok last week for JonBenet’s 1996 murder, blabbing to cops and reporters that he accidentally killed the little girl in an assault motivated by obsessive love for her.

A Thai official said Karr will be deported and sent back to the U.S. on a flight to Los Angeles this morning. “Generally he is fine, but a little bit nervous as the time of his departure approaches,” immigration police head Lt. Gen. Suwat Tumrongsiskul said.

Colorado authorities tracked him down after reading four years’ worth of twisted e-mails between Karr and Michael Tracey, 58, a University of Colorado journalism professor who has produced documentaries about JonBenet’s murder – and who tried to draw out more details about Karr through their hundreds of messages.

“You told me once that your mother tended to raise you as a girl,” Tracey wrote in one exchange obtained by the Rocky Mountain News. “This must have had a powerful effect on your developing sexuality – confusion maybe?”

“Michael, I will not discuss my sexuality as if it is a psychological disorder,” Karr wrote back under an alias.

The e-mails also show Karr felt a kinship with singer Michael Jackson – who has his own experiences with facial surgery and obsessive attachments to children.

“I am trapped in a world that does not understand,” Karr wrote. “I can understand people like Michael Jackson and feel sympathy when he suffers as he has. . . . I do think that he is sexually attracted to certain children but could never divulge this.” The exchanges began four years ago, after Karr met a Boulder writer when they were both staying in a hostel above a famous Paris bookstore. They immediately revealed his fixation on the pageant princess.

“Until he started talking about the Ramseys, he seemed perfectly normal,” Michael Sandrock, 48, told The News yesterday outside his home in the Boulder foothills, recalling his 2002 encounter with Karr.

“I didn’t get the feeling that he might have done it. I just thought he was obsessed about it,” Sandrock said. “I thought he was just someone who was fanatic about the case. But when I saw he got arrested, I wasn’t surprised. I don’t know whether he did it or not, but I could see where he had the potential.

Karr, who identified himself only as “John,” said he had been to Boulder and had come to Paris from Amsterdam. When he learned Sandrock was a sportswriter for the Boulder Daily Camera and a friend of Tracey, he wouldn’t stop talking about the case until Sandrock left a few days later – mentioning Boulder landmarks, obscure pieces of evidence, even names of reporters on the story.

“I’m really not interested in the case, and when I told John Karr that, he was kind of surprised,” Sandrock said. “I said, ‘I think the parents did it.’ He kind of just smiled and said, ‘The parents. Heh.’ ”

“I remember thinking this is just like from a Dostoevsky novel,” the writer said. “I always had the feeling that if I had pursued it more then, he was ready to tell me something. I just remember feeling that he was ready to unload, and it turned out Prof. Tracey was the one.”

Sandrock put Karr and Tracey in touch by e-mail, starting their four-year exchange. Investigators working for the Ramseys used routing information attached to the messages to track Karr to the Paris area this year, and they briefly considered tracking him down there to surreptitiously obtain a DNA sample from him.

“We had traced this guy back to France, and we were getting to the point where getting DNA was a possibility,” investigator John San Agustin told The News.

The Boulder County district attorney got involved in the case before they could travel to France, though, setting last week’s arrest in motion.

Karr was given a mouth-swab DNA test in Bangkok, according to a law enforcement official. He will be given another DNA test when he returns to the U.S., the official said.

Meanwhile, details emerged yesterday of an earlier chance to verify or discredit Karr’s claim that he killed the 6-year-old. The Sonoma County, Calif., sheriff’s department eyed him in the killing in 2001, when he was busted in a child porn case.

Karr’s lawyer at the time, Marie Case, said cops told her, ” ‘Hey, we’re looking at this guy.’ . . . There was possibly some involvement,” but inexplicably lost interest in him before testing his DNA. “Somebody dropped the ball,” Case told The Washington Post. “It never went anywhere.”

Boulder prosecutors have also been slow to try to corroborate Karr’s confession, the Denver Post reported yesterday, never talking to Sonoma officials, former employers or his ex-wife to compare his handwriting with the ransom note or determine his whereabouts on Dec. 26, 1996.

Meanwhile, JonBenet’s father, John Ramsey, was hounded by camera crews as he took his son to college at Purdue University, attorney Lin Wood said yesterday.

“He cannot go back to his home in Michigan because it is surrounded by the media. Last night, I’ve never heard him so angry. He is worried about his son’s physical safety.”