Asking for a friend: I know this group typically deals with people from Western nations but does anyone know the process for a Myanmar national to obtain permission to work in Thailand?

Since it's an ASEAN member, i'm not sure but my friend boss said they will obtain a work permission which can be renewed every 3 months at the Myawaddy border into Mae Sot. Once in Mae Sot, they can not leave the city. Seems to me to be shady and I just don't want my friend to end up in some kind of trouble.