The Labour Inspectorate is investigating a complaint by Mr Singh against his employer.
The sole director of DDPV Ltd is Dmitry Mochalkin, of Auckland.
Mr Singh alleges the company has failed to pay him entitlements worth more than $20,000.
He said he was owed leave, lieu days and about 230 hours of unpaid wages, among other entitlements.
Any wages he was paid by DDPV Ltd for work in Dunedin was at the minimum wage rate of $15.75 rather than the $18 an hour in his employment contract, he said.
After Mr Mochalkin failed to return his calls and emails, Mr Singh lodged an employment standards complaint about DDPV Ltd with the inspectorate, a department in the Ministry of Business, Innovation & Employment (MBIE), in July last year.
A new owner leased the station in November 22 last year and offered to employ him as a manager, if he got his work visa renewed. It was set to expire the following month.
He applied to Immigration New Zealand (INZ) but the visa application was declined because he had been out of work for three months and had failed to inform INZ, he said.
He had never been informed of the need to tell INZ when a job finished.
As INZ and the inspectorate were both part of MBIE, he believed his complaint to the inspectorate should have alerted INZ to his employment status.
As he wanted to stay in New Zealand to continue the battle against Mr Mochalkin, he applied to INZ for a tourist visa.
However, INZ told him on Friday his tourist visa application had been declined.
No reason for the decision was provided, he said.
By Tuesday, he has to show INZ he has booked a ticket to leave New Zealand before May 1, he said.
The length of the complaint process with the inspectorate was "frustrating'', especially since he had been "exploited'' when Mr Mochalkin continued to run service stations in the North Island, he said.
Mr Mochalkin did not return calls and emails from The Star before deadline.
Inspectorate regional manager Loua Ward said the inspectorate's investigation into DDPV Ltd was ongoing, so the case could not be discussed further.
However, if a director of a company failed to co-operate with an investigation "they open themselves up to the possibility of serious enforcement action'', she said.
In past cases, the inspectorate had secured money from non-compliant employers for former employees who no longer lived in New Zealand, she said.
INZ area manager Stephanie Greathead said some temporary work visas had conditions requiring the holder to work for a particular employer.
The visa label stated the applicant must work only for the employer specified.
If the visa holder wished to change employers they could apply to INZ if the new job was in the same geographical location.
INZ and the inspectorate worked "closely together to try and tackle the issue of migrant exploitation'' and had a memorandum of understanding allowing the agencies to share information, such as contact details and visa status.
