A former Singaporean lawyer now practising in Australia has been suspended by a Melbourne tribunal for five months, for professional misconduct - he billed a client about A$214,000 (S$217,000) in unauthorised fees and commission.

Peter Ng, 59, admitted to three charges, which included failing to declare that he was being probed by the Victorian Legal Services Commissioner when he applied for retrospective approval for the fees and commission.

"The serious nature of the offences indicate a personal flaw which must be addressed, thereby giving greater weight to personal deterrence," said Senior Member Gerard Butcher of the Victorian Civil and Administrative Tribunal.

"The need for personal deterrence is reinforced by the question of whether (he) has shown true remorse," he said in decision grounds released on Wednesday.

Mr Butcher raised doubts about this, though Ng had pleaded guilty and repaid the commission, which was "a financial disadvantage" to him.

However, said Mr Butcher, "given that he had no entitlement to the commission in the first place, such a submission has to indicate a lack of remorse".

Ng had been granted a power of attorney to manage the affairs of Mrs Gillian Littledyke in 2007.

A costs agreement at the time provided for legal fees of an estimated A$5,000 to A$6,000 per year.

But between 2008 and 2012, he charged her a total of A$44,505.

Mrs Littledyke was diagnosed with mild dementia in 2009, which Ng found out from her doctor in August 2012.

He then decided to charge a commission - made up of an establishment fee, annual fees and an "additional service fee". The commission was on top of the professional fees.

The annual fees charged were computed as a percentage of the annual value of Mrs Littledyke's assets; the establishment fee had a gross minimum value of A$3,000 while the additional service fee was up to A$360 per hour, payable when charged.

In the 2013 financial year and the first three quarters of the 2014 financial year, Ng charged a total of A$115,294 in fees or costs and A$99,848 in commission.

The fees charged were beyond the sums expressly authorised by the client and the commission was not authorised, the tribunal found.

Ng, a law graduate from the National University of Singapore, practised in Singapore from 1983 to 2004, except for a year.

He was admitted to the Victorian Bar in 1993, and commenced practice in Victoria, Australia, in 2004.

He did not refund the legal fees of about A$115,000 to Mrs Littledyke, though he repaid the total commission sum of A$99,848.

The tribunal noted that the legal fees were a "huge increase" over those charged between August 2008 and July 2012.

It also said Ng showed a "breathtaking lack of candour" when he included a 2012 letter addressed to Mrs Littledyke in his supporting affidavit without declaring that the letter was never actually sent.

"This lack of candour does no credit to the Court," said the tribunal, adding that the commission Ng took "can be seen as theft".

" This matter damages the reputation of the legal profession," it said.

The tribunal ordered the suspension to run from Sept 1 to Jan 31 next year and ordered him to pay A$8,500 in costs.