Phnom Penh is the capital city of Cambodia.
South towards Kampot, Sihanoukville
There is a roundabout called Choam Chao, 12 km from the city center or 2 km from the airport entrance. This is where the national roads NH3 and NH4 start, one to Kampot and one to Sihanoukville. This makes a good hitchhiking spot. A tuk-tuk from the train station will be between 2 US$ and 6 US$, depending on the time and how good you haggle. Bus number goes to the roundabout beginning at the Night Market.
Since late 2014 Phnom Penh now has a very small bus network of three routes. The most interesting is line 3 along Confederation de la Russie between the night market by the river in the east and past the airport to the Choam Chao roundabout. The bus is air-conditioned, comfortable, and not crowded. Tickets are KHR 1,500. Otherwise you can use Tuk-Tuks or motorbike-taxis to leave the city.