It's hard to understand why any foreigner or Thai for that matter would continue doing business with BKKB....gotta be the most non customer friendly bank in the whole world.
Either some other linked data is missing or the entry you're trying to make doesn't match with the type of visa you selected. I will agree with you that the online visa app is not very user friendly. Definitely not proofed by a Western educated professional. It's totally Thai style. Same in the US.
It's called VISA EXEMPT, it applies to 93 listed countries, the term is 60 days. If you leave the country it expires and you'll get a new one whenever you return. Theoretically you could continue doing that indefinitely, but I wouldn't chance it.
For $300 an agent will handle the whole process for you. No money in the bank no nothing. Done in 2 days. Multiple entry add $100. Work smarter not harder.
lots of Thai immigration things don't make sense. I always wonder why I can't just deposit all 12 months lump sum in January But I assure you the requirement is proof of 12 continuous months of income greater than 65,000 baht deposited to a Thai bank account, or a balance of 800K for 3 months prior and 3 months post the visa renewal date. .