On March the 5th myself and the mrs crossed the border from Thailand to Cambodia at Poipet, at the final barrier into Cambodia I was told to report to the Cambodian customs, which is on the left as you enter. I was met there by an official who told me I could not bring in my bike without prior approval from customs and a yellow book. Smelling a rat I said I would return to Thailand, but went into a noodle shop for a bit of lunch, the customs guy watched us as we fed. I then got on my bike and waited for the next big lorry and went along side obscuring custom guys view and continued to Siem Reap. There was another guy on a BMW with the same problem. On my way home 5 days later we went back through Poipet with no problem. So once you get through that final barrier, ride like you stole it, good advice I read on another thread.