What are the financial requirements for applying for a Non-O visa extension based on marriage in Thailand?

A UK passport holder currently on a Non-O extension based on retirement is seeking clarification on financial requirements for a marriage-based Non-O extension. They have deposited 400,000 baht in a new bank account and wonder if this amount, seasoned for three months, meets immigration's requirements, or if they must demonstrate a history of maintaining 800,000 baht in their account prior to the new application. Responses indicate that the 400,000 baht should suffice for the marriage extension as long as other documentation is properly prepared, although some regions operate with a practice of requiring three months seasoning.