@Flo****
, well, there are 70+ immigration offices inside this country, you don't say where he'll be, and each one has it's own quirks.
The rule is written to get a yearly extension based on retirement using monthly income method he needs to transfer in to the country from abroad a minimum of 65K baht per month, each month EVERY month for the preceding 12 months before he applies for an extension.
That's how it's written and following that at any office SHOULD be able to meet the proof of funds to get an extension