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).