Our bus adventure
I thought it might be useful to describe our bus trip from Saigon to Phnom Penh. We went with Kumho Samco Bus Line. There is a Kumho Samco forum thread which warns not to ride on this bus line. I think the people that wrote the post have never travelled in Asia before or had high expectations for their US$15 bus ride. Our newish bus was from the 1990s, it did the job. The seats were not the most comfortable but were bearable for the seven hour trip. It cost US$30 for two of us and we got a free bottle of water and free wi-fi on the bus. Others got their tickets on the bus cheaper but only by a few dollars. We also got a free taxi ride from the hotel we were staying at in Saigon with our luggage to the bus stop.
The first part of the journey is to the border. During the ride the conductor comes around and collects your passports and US$35 for the Cambodian visa. The conductor will not know any speak any English so do not spend your time in trying to ask for an explanation just go with the flow. You do not need a passport photo. We departed at 9.15 am and reached the border at 11.40am. You then exit the bus and go into the custom hall. Ignore the long line on your left and head to the front where it says foreigners. Here you wait until your name is called. They give you back your passport. A custom officer checks it. You then exit the building and give your passport back to the conductor who is waiting outside.
Back on to the bus and you travel a hundred metres to the Cambodian customs. You enter the custom building and sit and wait for the conductor to come back and return your passport with the visa. We only waited a few minutes. The visa was for a month. You then go through Cambodian customs where you are electronically fingerprinted and photographed. You then return to the bus for a short drive to the lunch stop. We shared a chicken and rice meal and survived. Then back on the bus. We left around 12.50. It is then a straight ride through, aside from the occasional stop for anyone who flags down the bus, in our case it happened just twice. We did not have a full bus. It is completely flat to Phnom Penh and you cross over a brand new golden bridge which replaces the ferry ride over the river. We arrived in Phnom Penh around 4pm so it took around 7 hours from start to finish and was quite bearable.
There are other bus companies and from what we have read some are better and some are worse. I thought Kumho Samco did the job quite well and the driver was not a maniac overtaking everything that moved.