You haven't said which of the 80 Thai embassies you applied at, you haven't stated the entry scheme you chose, nor your anticipated arrival date as asked during the application process.
If the LTR site is like other Thai evisa sites, you only get 1 document upload per category, so if you have multiple documents combine them into a single PDF
highlight the important data, dates, your name on the account, the 500K balance, to direct their attention to the relevant data. You do know it has to be in a single PDF file upload? Multiple uploads will replace/overwrite the previous upload
Probably it's more than a week old, you need to upload/submit the most recent statement/bank letter balance as possible. Typically signatures aren't required for application documents, the bank letter should be signed or stamped by the relevant bank officer.