if you use an agent there's a fee. If you don't want to pay the fee? Simple, do your own visa application. In Thailand it's not what you know! It's who. As the writer of the post stated he's stressed out.
I don't know where you are based? This agent is excellent at sorting out visas like yours without leaving the country. My good friend has used them for 18 years. If you have the 800k their service charge is good value for money. Maneerat Transport & Travel Visa and Tour service
The easiest way is to apply online to the Thai Embassy through their portal. If I remember I only had to show them one bank balance summary from my European account. It was a very easy process. I received my visa within 7 working days. A Non O. Arrived in Thailand within 60 days. Went to my local Immigration Office to register my Thai address 100THB again very easy. While in the office got the application to convert my visa to a marriage. Went to my local SCB opened an account in my name only. That was about it. I found the Royal Thai Immigration office very helpful and understanding. Here the portal link:
Yes I live here on we were in and out of Rayong immigration in 20 minutes.
When I applied for my visa three years ago. I used Royal Thai Embassy Portal. Got my visa in 5 working days. I use an insurance company in Thailand for my health insurance. Good luck with your move. It the right one.