I pulled a tourist visa from Seoul, that was a couple of years ago.
Often times when you take a teaching position the school will assist with the visa paperwork. You may want to contact the school. I believe some visas can be converted to non-b while others can not.
I forget what I paid for my volunteer visa but I am sure it was quite a bit more. My marriage visa cost LOTS more (wife, immigration paperwork, marriage paperwork, blah blah blah).
65K is a great prices to stay in Thailand. 180/baht a day.
The two reasons EDU visa haven't appeal to me.
A) Tests, immigration monitored progress
B) It may raise flags when entering Thailand. I had an immigration officer once tell me the EDU visa, isn't the best option for someone like myself (48 years old).