I noticed you said that you had not been living together for some time. If you have changed address, that would seem to trigger the need for a new TM30. In the process of doing that, immigration might well want photos or a home visit showing you living together, which would trigger the need to change Visa type.
Confirm that I have been using the year's print out from my Bangkok Bank account at Lopburi office for at least the past three years.......... (I do monthly remission method for a Non O based on retirement).
My practice is to prepare them a summary sheet listing all the International transfers by date and amount to add as a header to the print out. Also yellow marker highlighting the relevant entries on the yearly print. They LIKE that and use both during checking, completed swiftly as a result.
For monthly remission method, it is rare to have an exact coincidence of dates, the renewal usually takes place part way through a month, so the current month is incomplete. I simply provide evidence of 12 complete months up to the month preceding the renewal. They are fine with that.
I usually get the year print ordered and delivered a month prior. Then the final month pre renewal can be obtained on the spot in the branch. Slightly different format, but stamped signed and dated by the Bank and always accepted.
Last renewal was just on a month ago, completed in just on 40 minutes from in the door to out again, including filling out all forms in the office and a renewal of 90 days. On that occasion, no request for information on source of funds (UK accounts, pension letters etc) as has been the case in previous years. Nor any reference at all to my host Housemaster, who was present, but not a word addressed to him. I am well known and liked there, though, as is my family - 90 days done in person has advantages.......
I'm very clear that Lopburi office require 14 days prior to the expiry of the validity of the permission to stay, to process a 1 year extension of stay through ChaengWattana............ But you can apply up to a month ahead of expiry of the permission to stay.
ChaengWattana possibly will do it closer to the expiry date?
, my experience is that a 60 day extension - one only, or two, I forget - is available on the spot right up to the date of expiry of permission to stay. But that an application for a one year extension is required before 14 days before expiry of permission to stay.
I'm unclear whether the 60 day extension would reset the process of applying for that type of Visa, though......... That could require a trip out of country, on pre-COVID rules.........
But add to this post link the recent requirement for Health Insurance from a specified list of Thai providers if using route 2.
Route 3 is easiest long term, but needs careful preparation placing money in Thai accounts a fair while in advance - a year in advance if using the monthly remittance variant..