"I do not know the exact number this doctor has performed but it's in the hundreds," said Boonrueng Trireungworawat, ministry permanent secretary said. The doctor was not named.
Australian couple David Farnell and his wife Wendy made international headlines after a Thai woman they paid to bear their babies accused them of returning to Australia with the healthy baby girl while abandoning her twin brother Gammy, who has Down's Syndrome and other health problems.
Most of the cases involving illegal surrogacies in Thailand have stemmed from one clinic in central Bangkok, Boonreung said.
"While surrogacy is not illegal in Thailand, it is illegal for these clinics to offer these procedures without authorization from the ministry," he said.
Thai regulations permits surrogacy only between family members or close friends, where feasible. The regulation forbids the selling or renting of womb space for monetary gains.
Boonreung said the ministry was investigating the clinic. Those who have performed operations without the proper permits would have their medical licences revoked, Boonreung said. He added that the owner of the clinic would face criminal charges for medical malpractice and may face up to a year in jail.
Authorities in Australia were also seeking to assess the safety of the baby girl after reports that her biological father is a convicted child sex offender, news reports said. More details of 56-year-old Farnell's convictions emerged late Wednesday after the Supreme Court released records to media.
In 1997, he was jailed for three years on 18 counts of sexual assault against two girls, aged 7 and 10, in 1982 and 1983. In 1998, he was convicted on four counts of sexual assault involving a girl under 13. The then-married father of three children was sentenced to a total of four years and eight months.
"He's made mistakes," Farnell's son was quoted Thursday by Fairfax media as saying. "We've accepted it ... he's made up for it. For everything to be brought back up (is) pretty heartbreaking, to be honest."
The report said the son declined to be named.
West Australia's Child Protection Minister Helen Morton told The Australian newspaper that authorities were looking at how to deal with the case of the girl, including removing her from her parents.
"We are also interested in the child in Thailand ... for possible adoption and foster care for that child" in Australia, Morton was quoted as saying.