Thai police said on Monday they have questioned five women who were paid up to $12 500 each by a Japanese man known to them as “Jack” to act as surrogate mothers.
The baffling case, which emerged after nine babies were found with nannies in a Bangkok condominium, has triggered a human trafficking probe and intensified the focus on the kingdom's murky surrogacy industry.
The alleged father, who is reported by Japanese media to be the son of an IT millionaire, has left Thailand but last week voluntarily sent a DNA sample to try to clear his name.
The tests revealed he is the biological father of at least 15 babies born to surrogates in the kingdom, although his motives remain unclear.
“We have already questioned five surrogate mothers - there are six left to question,” Police Colonel Decha Promsuwan who is leading the investigation told AFP.
“They said they went through agencies... they wanted to do it because they could earn money, each of them was paid 300 000 - 400 000 baht ($9 300 - 12 500).”
Police have contacted their Japanese counterparts to learn more about the alleged father who was known to the surrogates as “Jack”, Decha added.
Thailand's shadowy commercial surrogacy industry was first thrust into the limelight following recent accusations that an Australian couple abandoned a baby born with Down's syndrome, but took his healthy twin sister.
The couple have denied deliberately leaving the boy, called Gammy, with the surrogate mother, who was paid around $15 000 to carry the twins.
Paid surrogacy is officially banned by the Thai Medical Council and authorities have since shuttered several IVF clinics pending a new law to tighten loopholes.
Tough penalties under the draft law could result in 10 years' imprisonment for involvement in the trade.
Dozens, possibly hundreds, of foreign couples are thought to have been left in limbo after entering into surrogacy arrangements through clinics in the kingdom.
Army Chief Prayut Chan-O-Cha, who was endorsed as prime minister by the Thai king on Monday, has tried to take the steam out of the issue, ordering authorities to act with “leniency on a case-by-case basis”.
His comments, come after Australia asked Thailand to make “transitional arrangements” to help its citizens who have already entered into surrogacy arrangements.
An Australian support group says 100 couples are currently going through a surrogacy process. - Sapa-AFP