Thai medical authorities are threatening to take legal action against a 21-year old Thai woman at the centre of global debate over the alleged abandoning of a Down syndrome baby by an Australian couple.

The Thai Ministry of Public Health says it is co-ordinating with other agencies in a crackdown against medical facilities and agencies linked to the commercial surrogacy the ministry calls “illegal”.

Thai reports said the ministry is also considering charges against the surrogate mother, Pattaramon Chanbua, a food stall seller from the southern province of Sri Racha.

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The ministry says the fact that Ms Pattaramon received payment of $15,000 as the surrogate mother was in contravention of Thailand’s human trafficking laws.

The Australian couple, from Bunbury in Western Australia, had denied the charge of abandoning the boy child, returning to Australia with his healthy twin sister.

The couple have charged that Ms Pattaramon “misled” the world over the events that led to them leaving the baby behind in Thailand.

But on Tuesday the Thai woman denied these charges.

“I have never lied or hidden anything. The truth is the truth; it’s up to society to make their own judgment,” Ms Pattaramon told Agence France Press (AFP).

Seven-month-old baby, Gammy, is receiving treatment at a Bangkok hospital where the child is being treated for a congenital heart condition.

A spokesman for the hospital said the baby was now receiving specialist care and is “in safe hands”.

Initially the Australian couple told the Nine network they had no knowledge of the other child, but in a statement released Tuesday said they were told of the baby’s existence but that it had a congenital heart condition and was not expected to live.

The case has spurred widespread debate, putting Thailand under the spotlight because of its weak legal framework overseeing surrogacy and in vitro-fertilisation (IVF) laws.

Thai law firm, Chaniwat and Leeds, which says it will cover surrogacy and IVF cases on its website, warns of possible “complicated legal issues”.

“While surrogacy in Thailand is currently an option and a rapidly-growing area of medical innovation, there are a number of legal considerations prospective parents should consider,” the firm said.

The lawyers said Thailand currently has no laws or published case decisions directly relating to the practice of surrogacy, “and in essence surrogacy is neither legal nor illegal in Thailand”.

Agencies and health clinics openly engage in locating surrogate mothers and egg donors.

“Thailand’s Medical Council has taken a cautious approach to the practices of IVF implantation, egg donation, and surrogacy; these practices are still in a legal and medical ‘grey area’,” the firm said.

Investigations are now under way by Thailand’s Bureau of Sanatorium and Art in Healing under the Department of Health Service Support (HSS) into the surrogacy service clinics.

There are reported to be an estimated 20 surrogacy agencies, most said to be foreign owned drawing in an estimated 4.0 billion baht ($A133 million) annually.