@David *********
Short reply: you're wrong with almost everything you said...
The requirement for the so called "Retirement visa" is age 50+, not "retired".
And of course he can work outside of Thailand, nobody at the Immigration care about, it's absolutely legal. He's not allowed to work inside / from inside the country.
There is definitely no rule saying the "income" has to be a pension, it absolutely doesn't matter how the money is generated... it can be anything... important is the sum, not the source.
For the first extension he needs to season the 800k... 2 month before application, 3 month after. Parallel he can start his monthly transfer of the 65k, so he can take out the 800k after one year.
Some Immigration offices in some provinces also allow to mix transfer with deposit in a Thai bank account, Phuket for example.
P.S.: His social security is a bit more than half of the requested sum, but okay... we don't know what will happen to the rate in the future...