I think I've been very lucky. Been using an agent who works for herself since I retired in Chiang Mai more than 8 years ago and she's great! She has charged me 1,500-2,000 over the years (and I always tip her 500) to do all of my paperwork beforehand and have someone wait in line early in the morning so I was always #1 when I showed up later. She knows everyone at immigration and knows the ropes. Also, anytime I have a question or problem during the year, she's there to help me out...no charge. I could renew my extension myself but she's like a friend now and I enjoy helping her and her family out...and getting great service in return. I would definitely recommend her to you if you were renewing in CM. If you find a good agent at a decent price, I think it's worth every baht you pay. FYI if I had to pay 10-20K like some others mentioned, I would do it myself.