"A caveat against using a visa agent.". He did not use a visa agent, he uses someone to forge fake stamps while not being in the system. When you use an agent you are inside the system (computer), legally, like everyone else.
Agent allows you to be hassle-free. I know the 60 days extension is 1.9k baht but it is location dependent. For a little bit more you can get it without any worry. You can also get other type of extension like medical, or visa like Non-O or Volunteer based on Non-O.
Kool Breez, if the agent says yes to take your passport, you will get the stamp no matter what. Agents are working hand and hand with some IO's. The deadline to transfer from Amnesty to Non-O via agent was around September 17-18, if you submitted after that you can only get Medical Visa due to lack of time. Agents know how long the process is.