Australian couple with twin girls born via a surrogate leave Thailand

An Australian couple with twin girls born via a surrogate has left Thailand after the ruling military leader called for leniency.

The couple had been raising funds via a charity website since the military crackdown began and were able to leave Bangkok with the twin girls on Monday night.

They were the third Australian couple to leave with babies born via surrogates since the ruling military revealed it was fast-tracking new surrogacy laws.

There is an estimated 150 Australians engaged in surrogacy arrangements in Thailand.

Prayuth Chan-ocha, the ruling army general who has been endorsed as the nation's prime minister, said until the new laws are enforced each arrangement should be considered on a case-by-case basis.

Thailand's surrogacy industry has come under scrutiny following accusations that an Australian couple abandoned a baby born with Down syndrome but took home 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.

In a separate case, police believe a Japanese man fathered at least 15 babies with surrogate mothers for unknown motives.

Earlier this month a gay Australian couple were stopped from leaving Thailand with a baby because they had incomplete documents.

Thai immigration officials said they could not disclose how many couples had been prevented from leaving Thailand with babies born to surrogates because they did not keep records.

Support group Surrogacy Australia said it knew of 100 couples who were going through the process in Thailand, which has long strived to be a hub of medical tourism.

Australia asked Thailand to make "transitional arrangements" to help its citizens who had entered into surrogacy arrangements.