No, Working is defined in the labor law, which is very clear and leaves no room for interpretation.
Yes, most of them are working illegally.
Look like you keep asking to find somebody to tell you that you can it legally, which you can't they way you like to do it. For a work permit you need either being employed or have your own business.
To get a work permit for while having your own business you need to employ 4 Thai staff for each foreigner you employ, including yourself.