Cambodia is still in progress to improve public transportation. I would not recommend you to rent a car or a motorbike and drive by yourself.
Traffic in Cambodia is terribly bad. It is sad to say but people don’t respect the traffic lights. They can come to you from anywhere on the road.
I would recommend you to pick up any of recommended transportation here:
There are Taxi available to bring you from any airport to the town. The cost will be set as a fixed price which is varied by airport.
In general, you would pay from $12 to $15 for a Taxi to get you from the airport to anywhere in town.
Those are the Airport Taxi community that well registered. They can take the Taxi straight away at the arrival area.
If you want to save money, you can try to request a pick up via these apps:
Phnom Penh city bus started their services to the public in 2014. There’s a bus station in front of the Phnom Penh International Airport. It will take you to town for less than $0.5.
The bus is popular transport if you want to move around from the capital to the provinces. The road in Cambodia is very busy. The people and animal cross the road without precaution.
It depends on how good the driver is to avoid the accident. So far Giant Ibis is the most recommend bus provider.
I also like to recommend the bus booking ticket BookMeBus.
A line of the train between Phnom Penh and Sihanoukville was opened for public in April 2016. It is a good opportunity to travel safe and enjoy the landscape of Cambodia countryside.
Visit their website for detail information and schedule: Royal Railways
In case an emergency or you want to go and explore Cambodia from the sky, there is a few helicopters provider in Cambodia.
I wrote a blog post about Helistar.