Yes, websites and email addresses ending with .tk, offering jobs, are usually scams.
I am sure that Tokelau, a territory of New Zealand located in the South Pacific, which owns this internet suffix .tk, has honest websites and email addresses, but if you receive an email ending with .tk, offering you a job, it's ok to assume that it's a scam.
Tokelau should ban the .tk domains that are used to commit fraud; but like Nigeria, they don't do anything about it.