South Australian father of four Nhut Chau Banh, 44, pleaded guilty in Horsham Magistrate's Court on Wednesday to speeding, having driven at a dangerous speed and having failed an oral fluid test.

Magistrate Richard Pithouse convicted and sentenced Banh to three months' jail, wholly suspended for two years.

He also convicted and fined Banh $500, ordered him to pay $71.40 statutory costs and disqualified him from driving in Victoria for two years.

Mr Pithouse said Banh's speed was 'extraordinary' and he had a 'complete lack of regard for the law'.

"You are very lucky you did not kill anyone on that day," he said.

Police prosecutor Sergeant Guin Cleminson told the court that a police officer saw Banh driving fast on the Western Highway at Dahlen, north-west of Horsham, on March 19 at 4.35pm.

The member measured Banh's speed at 175kmh in a 100kmh zone.

Banh returned a positive preliminary oral fluid test and provided an evidentiary sample in Horsham Police Station.

A further analysis showed methamphetamines.

Banh told police he did not take any drugs and he did not think he drove that fast.

Victoria Legal Aid solicitor Rita Sparham conceded her client had prior convictions in South Australia but he could not remember them.

Ms Sparham said Banh had depression, stress and anxiety and was driving a friend's car to Melbourne.

She said Banh had taken the drug a few days earlier with friends and was not a regular drug user.

Mr Pithouse told Banh he took a 'very, very serious' view of his misbehaviour.

"The explanation you gave to police was dishonest," he told the court.

"You have to be discouraged from behaving like that in the future.

"And the rest of the community needs to get a message as well, that the court will not tolerate this sort of behaviour."

A Vietnamese interpreter assisted Banh, of Torrensville, in court.