My understanding is that the retirement visa is determined only by reference to financial considerations and being over the age of fifty. Nothing else seems to matter.
Obviously, working in Thailand is totally forbidden for someone who had such a visa. The Thai authorities would have no way of knowing if the farang worked in another country nor do they seem to be the least bit interested whether he does or not. It doesn't seem logical to have a retirement visa, and commit funds to Thailand, if one is actually in employment elsewhere. Other types of visa might be more appropriate, especially in the case of a man married to a Thai woman. In reality, there seems to very little advantage in having a retirement visa if one is married. I appreciate that this is not the case for a single man who might be living with a Thai woman and, possibly, be the father of her child.
I haven't dealt with the multi-entry aspect. This is particularly complicated as it seems different criteria are used in granting visas outside of, and within, the Kingdom at present.