A Melbourne doctor who posted online that "some women deserve to be raped" has been suspended indefinitely amid an investigation by Australia's health regulator.

Christopher Kwan Chen Lee was in April found guilty of professional misconduct and suspended for six weeks by the Tasmanian Health Practitioners Tribunal for making a series of disrespectful and racist comments.

The suspension, due to expire on June 11, was extended by the Medical Board of Australia as of Thursday.

"The board has taken this action in the public interest to maintain confidence in the medical profession," it said in a statement on Friday,

Dr Lee was employed in Tasmania for two years from February 2016, and was in early 2019 working as a registrar at Box Hill in Victoria.

He was prolific in a Singaporean chat room where in 2016 he wrote that "some women deserve to be raped, and that supercilious little bitch fits the bill in every way".

Dr Lee said the post was made in the context of a Singapore/Malaysian political situation after a female college student made disparaging remarks about servicemen.

Dr Lee described himself online as a "mongrel doctor".

"I will not conform to your ridiculous moral standards and your expectations of what a doctor should or should not say," he wrote in December 2016.

"I am a medical practitioner. I also have a foul mouth and call a spade a spade."

He also posted in January of that year:"If my marriage fell apart, it would not end in divorce. It would end in murder".

In his April 17 decision, tribunal chairman Robert Webster said Dr Lee's comments were "disrespectful of women", "racially discriminatory" and had "potential to cause harm to the public".

Dr Lee had worked at the Royal Hobart Hospital and a hospital in Traralgon in Victoria's Gippsland region.

The Medical Board of Australia does not have the power to deregister a practitioner - the decision can only be made by an independent tribunal.

The board is currently investigating Dr Lee's behaviour.