It clearly states it is NOT a visa. It is a free arrival info card done online. Done during the 3 days prior to arrival. What's difficult? Your name, passport, country, date of arriving, address of accomodation etc.
Your first year's extension you need the 800k in the bank and also during that year you also do 12 months of 65k each month EVERY month. So, that on the second year you can switch to the 12 deposits of 65k method EVERY month, without the 800k .
You've been trying to enter repeatedly as a tourist, ( but trying to live in Thailand because you've got a girlfriend?)so that's why you've been stopped.
When I opened my bank account they asked for UK ID card and passport. We don't have ID cards ( not since just after the war ). I gave them my seniors bus pass, which had my county's govt address on it and my photo. Convinced them it was equivalent of an ID card. 😆