Can I transfer money between bank accounts during the seasoning period for a Thai marriage visa extension?

Definitely wait. When the rule says “A” bank account you have to keep two things in mind. One is that many things don’t translate well to English. The other is that rules in Thailand - especially in immigration - are whatever the person you are standing before says they are. So I agree with the sentiment to not make it any harder than it needs to be! I wouldn’t even ask ahead of time because if they say it’s fine then, there is no guarantee you will get the same answer when you go back 2 months later (or 2 days for that matter.)

Why not just wait ? It’s 2 months not 2 years

No

Simple advice is don't make things any more difficult than they already are.

I'd almost bet that the immigration office isn't gonna accept it because you "broke the chain" (moving it from one bank account to a separate account at a different bank). I know they have given people grief for moving it from one account to another INSIDE the same bank branch

I'd say don't do it.

OR

Go to your immigration office with your thai wife and ask them specifically if it can be done (before you move the money) or if doing it will mess up your seasoning.