Just read this and thought useful for some who deal with Bangkok Bank
Bangkok bank told us that since 1 July, they require you to have the money in your account for 4 months (!!), before they can issue a letter that confirms proof of funds for various visas. And if you do not meet this 4 month requirement, they will lock the funds in your account for an additional 4 months, before you can access it; while giving you the right papers that you need for immigration (proof of funds for 2 months). Its not an immigration or visa requirement, but rather a banking requirement to deter money laundering and people using agents (that is what they told us)
TLDR : Answer Summary
Since July 1st, Bangkok Bank has implemented a new banking policy requiring account holders to maintain their funds for at least four months before the bank issues a letter of proof of funds necessary for various visa types. If an account holder does not meet this requirement, the funds will be locked for an additional four months, though this does not align with immigration requirements, as it is a banking measure aimed at preventing money laundering and the use of agents for visa applications. This has caused confusion and concern among expats, especially those looking to extend their visas.