Mate, your statement "A work permit can be cancelled anytime, and thus it has no expiry date" is incorrect as extension of the regular work permit is required at Department of Employment (just like the non b visa).
don't know about the palatial home in the middle of a rice field... but isn't the reason for 'selling assets in their home country' to avoid taxation? Where I'm from government is always very short of cash and actively looking for sitting ducks and easy targets 😉
Yes!! getting long-stay visa for work is difficult but it is not totally impossible like someone else said.
You do need the qualifications / education and job-experience to be able to get a job in Thailand, and get the sponsorship from your company for the Non-B visa and work-permit application.
One possible approach is getting an expat-assignment in France, in case he works for a company in France that has offices in Thailand and they're willing to help you. Becoming a TEFL teacher is probably one of the easiest approaches but (unless he is highly qualified) the salary and job can be challenging. The website ajarn.com has info about teaching jobs and what people (don't) like about it.
Also, there is the newer SMART visa's for specific highly qualified staff. Some generic info you can read here:
If the OP is to lazy to perform the most basic check and resorting for FB for advise, I'm inclined to make an exception that BS is very well deserved in this situation..