Some are saying, showing the cash in your bank app is ok or with a certified bank statement. I checked with the London Thai embassy, they said cash only. I just bring cash in different currencies.
It is 20k THB for a single visitor and that has always been the case for tourists before the DTV was issued. DTV comes under tourism but the recent changes are aimed at those abusing the VE system.
Visa processing time is 10 working days excluding the day of submission. Dec 5, 10 Thai holidays. In addition, embassies are busier due to the high season and recent changes,
Yes certification involves a bank stamp and signature. I read 3 months bank statement is accepted. On UK embassy website there is no mention of statements being acceptable though just cash. so for myself I just stick with cash. Double check with your embassy regarding the statements