Can my wife and I switch visa extension justification methods after the first year in Thailand?

Might work, remember you (as the trailing spouse the first year) need to get the Non-O visa outside thailand seeing as they don't issue that visa for people married to retirees.

If I understand you correctly

the first yearly extension from the Non-O visas would be your wife, using the 800K baht banked money method and you as the 'trailing spouse'. <-keep in mind that 800K baht needs to be in the account 2 months before she applies for the year extension, it has to stay IN the account for 3 months after she gets the extension granted and then the balance can't go below 400K baht the rest of the year <- that's until you apply for a new extension the following year.

and you will be transferring in 65K baht a month each month every month so that next year you will have 12 months of transfers and change the reason for your extension to one based on retirement using monthly transfers and your wife will then become the trailing spouse without any fund requirements (other than the ones on the banked money from her previous extension)

As I said it COULD work, but it sure is convoluted. Why not just transfer the funds into your bank account you get the banked money extension and let her be the trailing spouse and then start bringing in the monthly transfers into your account and change the method of proof of funds the following year, rather than trying to take one person off the retirement extension to trailing spouse and the other one off of trailing spouse to retirement?