"The way Wall Street is to finance -- Bangkok is to pedophiles."
That's the way Thailand's capital was described by an unidentified man who spoke to ABC's "Primetime."
So far, John Mark Karr has not revealed why he came to Bangkok to live.
He worked for a short time as a teacher in a Thai primary school before being dismissed.
Now, Karr's arrest here has cast a glaring spotlight on the secret world that's not so secret -- and continues to spread throughout Asia.
Children are often sold or forced by their families into prostitution, sometimes as young as 6 years old.
Psychoanalyst Bethany Marshall says her pedophile clients are intrigued by recent news of Karr and the discovery that he was living in Thailand.
"In the United States, in order for the pedophile to get in bed with the child -- metaphorically -- he has to get in bed with the entire family as well. It's not the same in Thailand. Because of the sex trade, you can get in bed with the child literally and not have to entangle yourself with the family. In fact, it should come as no surprise."
Every day, there are thousands of foreign men in bars or walking the streets of Bangkok looking for sexual encounters with Asian women.
According to one group fighting sexual exploitation of children, there are at least 5,000 foreign men coming here every year, looking to have sex with children.
Thailand is not alone.
Cambodia, Indonesia, Vietnam and the Philippines have thriving businesses in underage prostitution.
Apparently, not much has changed from when ABC's "Primetime Live" went undercover here in the 1990s, and revealed how children could be rented for $80 a night.
Since 2003, when the U.S. Child Protection Act was signed, 29 Americans have been extradited and convicted for abusing children.
Half of those cases were in Asia.