I provide an address that looks technically correct, ensure it’s delivered with DHL, and then override DHL to pick up at one of their locations.

Also, there are special delivery companies like CamboQuick that take the whole process out of your hands and use (slow) ships freight to ship stuff from Amazon et al to Cambodia. You’ll have to wait 4-6 weeks, but they handle the custom clearance and everything and deliver it to your house for a $2 fee.