* Says doctors knew in fourth month, told her in seventh
* Baby needs heart surgery, online campaign collects funds
* Case prompts calls to end commercial surrogacy in Thailand
By Juarawee Kittsilpa
BANGKOK, Aug 3 (Reuters) - A Thai surrogate mother left with one twin by his Australian biological parents after the child was born with Down's Syndrome said on Sunday she was not informed of his condition until late in her pregnancy.
Pattaramon Janbua said her doctors, the surrogacy agency and the baby's parents knew he was disabled at four months but did not inform her until the seventh month when the agency asked her - at the parents' request - to abort the disabled foetus.
Pattaramon, 21, told Reuters Television she refused the abortion on religious grounds and carried both him and his twin sister to term six months ago. The parents, who have not been identified, took only the girl back with them to Australia.
The boy, Gammy, needs surgery for a congenital heart condition, according to media reports. An online campaign in Australia had raised nearly A$200,000 ($186,200) in donations so far for the operation.
"I want to warn those who are considering becoming a surrogate mother, don't only think about the money," Pattaramon said. "If the child is born with an unusual condition or if anything goes wrong, it will become a burden for you and society."
The case has caused controversy in both Thailand and Australia and brought calls for commercial surrogacy to be banned in the Southeast Asian country. Thailand is a top destination for medical tourism and many couples come for services such as fertility treatment and some for surrogacy.
Australian Prime Minister Tony Abbott said on Saturday that authorities there would look to see if there was anything they could do about the case. "It is an incredibly sad story," he told Australian reporters.
Pattaramon said she agreed to a fee of 350,000 Thai baht ($10,900) to carry the twins for the couple. She said they agreed to pay her another 150,000 baht to keep Gammy.
She declined to identify the agency or give details of the providers of medical services to her during the pregnancy.
Gammy is being treated for a lung infection in a hospital east of Bangkok and his condition is stable, a spokesman as the hospital said on Sunday.
There are no laws governing surrogacy in Thailand, said Vichien Chavalit, permanent secretary of Thailand's Ministry of Social Development and Human Security. A law has been drafted but not yet submitted to parliament.
Gammy was not the first case in which a child has been left with a surrogate mother, Vichien said, adding: "This will lead to further social problems."
Lawmaking in Thailand has been paralysed since December, when parliament was suspended by then Prime Minister Yingluck Shinawatra. She was forced from government amid mass protests in Bangkok shortly before the military staged a coup on May 22.
The military government named an interim legislative assembly on Thursday and it is expected to hold its inaugural sitting on Aug. 7. (Additional reporting by Apornrath Phoonphongphiphat and Morag MacKinnon; Writing by Simon Webb; Editing by Tom Heneghan)