Details of the "toxic relationship" between Han's Cafe founders Ian and Tram Han have been laid bare during a Federal Court hearing into the Thai food chain's underpaying of staff.

The once 20-strong restaurant chain's management company, Han Investments Pty Ltd has collapsed but 12 of the franchised cafes remain in business, with Mrs Han still earning around $20,000 a month in franchisor income.

The Han's met in a Thai refugee camp and built one of Perth's most successful Asian food chains in the 90s, with the couple soon becoming millionaires.

But their business began to unravel in 2014 when the pair separated amid allegations Mrs Han was the victim of ongoing domestic violence, with Mr Han "fleeing" Australia in early January 2015, leaving Ms Han to manage the business and raise their two young children.

The Federal Court of Australia, on Wednesday, found Mrs Han had breached Fair Work regulations by failing to pay staff wages totalling $30,000 to 27 staff members in 2014. The business also failed to keep timesheet records of hours worked by staff.

She told the Fair Work Ombudsman at the time she would have to close her business if she was forced to pay weekend penalty rates - as required under the restaurant award.

Mrs Han pleaded with the FWO to consider her difficult personal circumstances when determining a penalty, and that she was "doing her best" to run the businesses on her own.

Justice Michael Barker, however, in his judgement handed down on Wednesday, described the contraventions of the Fair Work Act as serious.

"I consider that the various medical reports submitted on behalf of Mrs Han are relevant to the question of the assessment of penalty of behalf of all respondents, including Mrs Han," he said.

"But having read them, they do not fully explain the conduct of their conduct.

"It is not said, for example, that Mrs Han was unable to meet the requirements of the FW Act and FW Regulations because of her distress."

Hans Investments was fined $45,000 while Mrs Han was fined $7,500 for not complying with the Fair Work Act. 

Originally published on WA Today as Han's Cafe fined, collapses amid domestic violence claims .