BANGKOK - A surrogate mother is seeking help from Thai authorities to get the infant back from his American father because she suspects he is her biological son, a news report said on Tuesday.

The case is the latest controversy to emerge from the country's surrogacy industry, after an Australian couple were accused of abandoning their surrogate baby with Down syndrome last year and a Japanese man was found to have fathered at least 16 babies with surrogate mothers for unknown motives.

Thailand's interim parliament last month passed a law that bans foreigners from seeking surrogacy services to end the "rent-a-womb" industry, but the ban will come into force only 90 days later and cannot be applied retroactively.

The 34-year-old woman in the latest controversy, who cannot be named, wants to get back the baby she gave birth to in January because she says he could be her biological son, The Nation reported.

"How do I know if it was my egg or someone else's egg? I can't be sure. So, I want the baby back," she was quoted by the Nation as saying.

The woman said she had been recruited by an agent to serve as a surrogate mother for an American man in his 40s.

She was treated at a clinic run by Dr Pisit Tantiwattanakul, the same doctor who allegedly allowed the Japanese man, 24-year-old Mitsutoki Shigeta, to hire multiple Thai women to bear his children, said The Nation.

According to the report, the surrogacy contract involved a six-digit baht payment plus a monthly allowance of Bt14,000 (S$590) during the pregnancy. After the woman gave birth to the baby, the man never contacted her again.

"We have already alerted the US embassy here to help prevent the father from taking the baby out of Thailand," said Verutai Maneenuchnate, an executive director at the Women Lawyers' Association of Thailand.

The surrogacy transaction constituted human trafficking and should be void, Verutai said.

Verutai on Monday took the woman to National Legislative Assembly (NLA) member Wallop Tangkananurak to ask for help. Wallop chairs the NLA committee on society and women and children affairs. He said his committee had set up a subcommittee to look into surrogacy issues.

"It will handle many cases including the one involving the Japanese man," he said. The man had not been seen in Thailand since Aug 7.