By bus

The TAT offices in Bangkok will organise your journey to Siem Riep. The first part, by air-con mini-bus takes you to the Thai side of the border and is relatively pain-free.

On the Cambodian side of the border (Poipet) you pick up a slightly less luxurious bus to Siem Riep, but the journey is not for the faint hearted.  It takes anything from 5 to 9 hours depending on the weather as no part of the journey is on a sealed road. Some parts of the roads have holes deeper than the bus, but its character building!