Yes people used these in the past in Asia and Immigration, the embasseys and the schools were too lazy to check them. That has changed in Korea. Degrees or transcripts have to be mailed now from the home university and received by Imigration unopened. They keep legit examples on file.
Sure you can still fake it with friends back home etc. but if caught all your earnings/baggage can be confiscated (I have seen it done to a Romanian) and you have a criminal record that is international. Much safer to go to these countries on a tourist visa and do what you will. Canadians can stay 6 months on a tourist visa as Canada reciprocates with 6 monthd for Korean tourists. I suggest all teachers go to Asia on a tourist visa to check out the school first. Don't buy a pig in a poke or more to the subject: Don't work for a pig in a poke.