One more thought is that Siem Reap has a new transportation option call PassApp. It works like GrabTaxi (they have that as well) but you can choose type of vehicle as in Tuktuk, car, or rickshaw. The rickshaw is, similar to a Tuktuk but it is smaller and cheaper. It is enclosed cab. Fare is determined by the app not the driver and displayed to you after the trip is completed.