I admit, I wasn"t aware this was a thing with medical Doctors.
There are so many different models for funding pilot licenses. An acceptable ATPL is expensive to get, but then so is a degree. In various countries, tertiary education is free, in others, it needs to be paid for either up front, during or recovered later in life.
2000 unemployed Thai pilots (it doesn't seem clear to me if they are ATPL) seems indicative of lack of internationally recognised appropriately type rated license, or perhaps English language skills, making employability outside Thailand problematic.
Many airlines are looking for pilots, just not in Thailand... as can be seen by the wet lease model. (This is simplification of wet lease, of course.)
In regard to the medical requirements for retired pilots who instruct only in simulators, perhaps this should be looked at, but.... To instruct means keeping current.... Can an instructor be a person who no longer holds a current type rated pilot license, (medical requirements) or could there be a different requirement for ground instructors?
Aircraft maintenance training schools don't require their instructors to be aircraft maintenance engineers and not all ex AMEs make competent instructors...