What are the document requirements for a Non-O (spouse) visa extension at Immigration Chaengwattana, and how does Bangkok Bank handle balance confirmation letters?

Today my spouse and I went to the Immigration Chaengwattana to inquire about required documents for the first one year's extension of Non-O (spouse) visa. We also visited Bangkok Bank branch downstairs to check about getting a statement and balance-confirmation letter from them.

We were told that if we have already had the required amount sit in the account for four months, we can have those two documents right away with no conditions whatsoever. Otherwise, they will issue the documents but will freeze that amount in the account for four months, starting from the date of issuance.

Does anyone know if any other banks also do this? (I know that Krungsri doesn't -- at least not yet -- because we went in to ask also.)

Will this become standard in the future? HOPE NOT!