BBC News also came across hundreds of posts from people openly stating they were in the country illegally and looking for nail bar jobs.
Posing as a Vietnamese skilled nail technician in the UK without a visa, a team member called a dozen nail bars to see if they would give her work.
Within an hour she had two job offers.
The employers seemed more concerned about the technician being able to do the job rather than whether they had the documentation to work legally.
Hourly rates varied depending on level of experience – basic skills could earn about £30 per day whereas experienced technicians could make up to £160 per day.
Other businesses said they were not taking on staff without papers as it was “too risky”.
More than 30,000 people crossed the Channel in small boats this year, with Vietnam making up the fourth largest group – behind Afghanistan, Iran and Syria – with 3,307 arrivals in the year to September 2024.
Many Vietnamese migrants have told the BBC they came to the UK seeking work because of failing businesses and debts. Their first step, experts have suggested, is often to access Europe by taking advantage of a legal work visa system in Hungary and other parts of Eastern Europe.
Experts told BBC News that many of the people working in nail bars illegally are victims of modern slavery.
“The people who are making the crossing into the UK will often have to pay either through extortion or from being exploited in some form of forced labour or criminality once they arrive,” said Jamie Fookes from Anti-Slavery International.