Thai police said have found four more babies they suspect were fathered by a Japanese businessman who has fled from Thailand, bringing the total to 13 discovered in Bangkok this week.
Surrogacy scandals have gripped Thailand this week after an international outcry over a Down Syndrome baby left with his Thai birth mother when his Australian biological parents took his twin sister back to Australia.
In a separate case, police raided a condominium in Bangkok on Tuesday and found nine surrogate babies, their nannies and a pregnant surrogate mother.
On Friday, police found four more babies though they did not give details about their health or say where they were found.
''He is the father of 13 surrogate babies and has been travelling in and out of Bangkok many times,'' Police Colonel Napunwut Liamsanguan said, referring to the unidentified Japanese man.
The scandals have shone an international spotlight on Thailand's largely unregulated surrogacy business, prompting authorities to crack down on clinics with nationwide inspections
Liamsanguan said police raided a clinic in Bangkok believed to have been used for in vitro fertilisation (IVF) for the 13 surrogate babies after being tipped off by one of the surrogate mothers.
The clinic had been vacated and no documents had been left behind, according to police.
Thailand has no clear legal framework for surrogacy.
Commercial surrogacy is barred by the Medical Council of Thailand's code of conduct.
Surrogacy for no financial gain is permitted for blood relatives of a couple, and exceptions are allowed on a case-by-case basis.
The clinic raided on Friday had a license to perform IVF for surrogacy purposes but the police said they suspected it had violated the code of conduct.
The clinic's head doctor could face up to one year in prison and a fine of up to 20,000 baht ($622), if found guilty.
The unidentified doctor owns another clinic that was also raided by police on Friday.
If it is found to have no medical license to perform surrogacy, he faces an additional three years in prison and a fine of up to $1,870.
The Australian couple, who have come under heavy criticism for apparently rejecting the disabled boy, have remained silent, but were expected to speak to an Australian television network on Sunday.
The case of "Baby Gammy'' - as the boy is known - has provoked an international outcry and shines a spotlight on Thailand's largely unregulated surrogacy business.
Gammy, now seven months old, is being treated for a lung infection in hospital. He also has heart problems.
A draft law banning commercial surrogacy has been submitted to the military government's head of legal affairs, Rarinthip Sirorat, an executive from the Social Development and Human Security Ministry, told reporters on Thursday.
The draft law would ban commercial surrogacy and those found to have violated the law could face up to 10 years in prison and a fine of up to 200,000 baht ($6,200).
Thailand has 45 licensed surrogacy clinics, 12 of them in Bangkok, according to the Ministry of Public Health, and 240 people have a medical license to perform in vitro fertilization (IVF) for surrogacy.