Correct, there are only 2 financial proofs you can use for the FIRST 1-year extension.
1) embassy certified proof of monthly income
2) proof of 800,000 baht in your Thai bank account
In order to use #2, the money must be in your account for 2 full months already at the time you apply for the extension.
For full details, you need to go to your immigration office, and ask them for their handout for a retirement extension. That will have the specific requirements for your immigration office as they vary from office to office.
It doesn't hurt to ask if you can use monthly transfers, but I've yet to see someone able to do that.
the only thing they will accept if they ask for proof of funds is cash. They will not accept bank statement, bank apps, credit cards or debit cards. Also know that for the major airports there is no ATM machine between the plane and the immigration checkpoint.
just know it's very, very difficult to get an insurance company to sign this. Many people end up having to purchase one of the policies from the approved list of Thai insurance companies because of that
agents don't know the rules either when they're changing fast. And most agents only know the rules for the single immigration office they work with. Plus they get to ignore many of the rules so don't know the actual rules
There's no such thing as a 1-year non-O visa. You might have had a visa at one point, but you're on an extension of stay now.
Is your current extension of stay based on being a dependant of your husband who has a work extension?
There's absolutely no reason changing companies would take 4 or 5 months.
If your husband plans to stop working then both his and your extension will be invalid the moment he ceases employment and he will have to cancel the extension as of that date.
If he's just transitioning from one job to another, then his work extension can remain valid as long as he changes his work permit from one job to the other seamlessly.