I'm not quite sure if he could come back, as mentioned by others there is maybe a note. We can't affirm he was denied for it but, he certainly may get issues continuing this way.
Not even ED... With all his "qualifications" (visa, relocation, real estate, etc.), he can directly apply for a work permit, but all of this may still fall under the list of prohibited work.
Anonymous participant 445 You're clearly involved into relocation consulting, thai visas and real estate. Thus, working illegally without a work permit.
It doesn't matter if your clients are foreigners and the money goes abroad; you're offering consultancy services on Thai visas, which are linked to the Thai government and therefore prohibited. The same applies to relocation services and real estate; if you are dealing with Thai entities, you will need a work permit, and such activities are strictly prohibited under a DTV.