Extension of stay based on lump sum deposit (Married to Thai) - (and couple of other related questions, cos I not use that extension method for years) ?

Before I use the affidavit from Embassy and evidence of monthly transfers. However, because of difficulties related to overseas transfer bank code etc., I decided to switch to lump sum 400k deposit.

Where I may find example of bank letter (Bangkok Bank if this important)?

Should I get this letter a day before application?

The lump sum must be deposited 2 months before application - is this still correct, and how these months are calculated? For example, If I deposited funds at the end of December, will be good to apply in the first days March, or I should calculate some amounts of day (for example, funds deposited on 22 December + 60 days, good to apply on 22 February)?

On the day to get final stamp, should I transfer some small amount to account then update bank book to show the funds still at account?

Thank you so much