On July 10, 2017, we have tried in vain to enter Cambodia via Poi Pet using our Singapore registered car, Thai and Cambodia official both warned us before hand, but we still gave it a shot, but failed spectacularly, end up doing a u turn back to Thailand, and up paying 1200 thb for the official to expedite the process of clearance.
Now that I've came across this posting, I'm kicking myself in the butt for not doing more research, and that would have saved me the hassle just by going thru O'smach. GRRRRR!!!!
Gonna give it one more try in time to come, but now that I have changed my SUV, I need to redo the suspension and alignment set up in my SUV to be able to travel overland with all that luggage, tools and spare fuel.