A few weeks ago, my visa agent alerted me to go to my account opening Bangkok Bank branch to verify and update all my details. I provided my passport copy, residence certificate copy, Thai driver’s license, home country ID and driver’s licence. Signed a bunch of forms too. Basically to give proof to show I am who I say I am.
Looks like you have your finance in order now. Just ensure the 800k is there 4 months before your renewal visa date and 3 months after. Maintain a minimum of 400k outside this timeframe.
Alternatively, just always leave 800k minimum in the account.