Edited:If you make it thru on a Visa Exempt then get your 30 day extension here-> then use a Visa agent out of Bangkok such as Thai Visa Service to do a border bounce to Cambodia to repeat the process. This agent will secure you another Visa Exempt up to a maximum of 2/calendar year, as it will be 2023 by then you are good to go on this option.
One day is enough. If you have many stamps and long stay here as a tourist I would recommend using a Visa Company from Pattaya. Avoid Poipet border crossing.
If you just want to stay here and not study you could almost stretch tourist Visas to one year. I believe the Multi Entry TR Visa if done correctly can net you 6 months then 2x border bounce with an agent to Cambodia gets you another 75x2 = 150 days. This'll run you around 15,000bht for 11-12 months, but more complicated.
Rubbish - They want you to use them to get a bank account. OR so you can transfer the Fee for the Service to their bank account. Consider using another Agency and going to Cambodia and get the Visa Exemption 45 +30 (only 15 days less than the TR90, plus only takes one full day to do the Exemption border bounce).