The article about riding a motorcycle on the Chiang Rai loop is inspiring me to do the same trip. Has anyone else done this trip? Where should I rent the motorcycle from in Chiang Rai? I plan on going the middle of December. Any help/advice would be greatly appreciated.
Check out the GT Rider site (Golden Triangle RIder.) It has pretty much everything you need to know for motorcycle touring around Thailand, including how and where to rent bikes.
Yeah I've done the trip (I wrote the story ;-) I just did it on a 100cc Honda Dream -- every man and his dog in Chiang Rai will rent you one for 100-200B a day.
Generally you'll be asked to leave your passport with the agency -- I always have and have never had a problem. Some get away with just leaving a photocopy of the passport, but that decision is down to the hiring agency.