Chris Guon was investigated by the Fair Work Ombudsman after two employees at his franchise of the 678 Korean BBQ chain claimed they had been paid a flat rate of $11 to $13 an hour.

Fair Work inspectors found the pair, who were both on 417 working holiday visas, had been underpaid over $1300 between December 2013 and June 2014 at the Pitt Street restaurant.

An investigation uncovered that Mr Guon's KPG Au Group Pty Ltd had advertised for staff on Korean websites offering pay of $12 to $16 an hour.

The ombudsman's office said that when questioned about the advertisements, Mr Guon claimed there was pressure from other Korean businesses in Sydney not to offer more than the going rate.

He said businesses that did not comply feared having false claims about food hygiene made to local councils.

Mr Guon had not kept proper paperwork, which hampered the investigation, but the ombudsman ultimately ordered him to repay the workers, who have both returned to Korea, $661 and $642 in owed penalty rates.

Mr Guon also received a $1700 on-the-spot fine for not issuing payslips, and ordered to implement a workplace relations training program and to undergo an external audit of his workplace relations compliance.

His restaurant must also display notices in Korean and English detailing the breaches.

Ombudsman Natalie James said her office had recently come across a number of Korean businesses recruiting and underpaying Korean nationals, and that 10 per cent of all requests for help from employees were coming from foreign nationals.

Ms James said her office had launched a pilot program to engage multicultural communities and help migrant workers and international students understand their rights at work.

"We take a dim view of any employer who seeks to profit by underpaying their staff, particularly vulnerable overseas workers," she said.

"Whether you're a business owner or an employee, workers that have come from overseas have the same rights as local workers and should be treated with dignity and respect.'