What are the renewal and bank seasoning requirements for a Non-Immigrant O spousal visa in Thailand?

Most offices allow you to apply for a new extension when you have 30 days or less left on your current stamp (Some offices Bangkok, Chiang Mai, Phuket, etc allow you to do it when you have 45 days or less left ony our current stamp)

There is no 3 month seasoning (no matter what anyone tells you even if it's an immigration officer) The seasoning requirement on the banked money method for a yearly extension based on marriage is the 400K baht has to be in a thai bank account in your name only for 2 months before you APPLY for your next extension.

That can be 400K baht or the equivalent in GBP in a thai bank account in your name

As far as can it be a term deposit <- in thailand there are two types of "fixed" or "term" deposits

One is where you can access the funds at any time (even if you incur a penalty or lose interest) <- this account you CAN use for proof of funds

The other is where you cannot access the funds only the interest earned on it and the 400K is frozen in the account for the term of the deposit <- this account you CANNOT use for proof of funds.

You can't use stocks as proof of funds