Thailand Aranyapathet to Cambodia Poipet Border Crossing
This is a trip that perhaps the majority of travellers will undertake if they are going to travel the Indo China/SE Asia loupe (Thailand > Cambodia > Vietnam > Laos). There are 2 border crossing into Cambodia , one being in the south Trat which perhaps is a little more complicated as boats etc are involved and the other is Aranyapathet to Poipet.
To opt for the later option a full day is recommended with a very early start. If you are travelling from Bangkok it is definitely possible to reach Siam Reap in a day, although it will be a long day. You will need to catch a bus from the Northern Bangkok bus terminal Mo Chit and it is highly recommended that you catch the 6am maybe 7am bus to Aranyapathet. Catching local busses are cheap and good fun as you get to meet the locals. You should be in Aranyapathet around lunch time. As you get there you will come across many people trying to sell tickets to Siam Reap, just wait to get over the border before you decide which agent to go with assuming you are going to Siam Reap. This is also a very poor area so it may come as a little shock to you if you have not seen any really poor people/areas yet.
There will probably be large cues for immigration both on the Thai side and Cambodian side so you will have to wait in line. You will probably be buying a visa on the border and this is definitely possible but the Cambodian Officials will definitely fleece you. I really can't remember how much I paid but got fleeced for something like $8 - $10 US.
Once over the border the first thing you will notice is the smell, the rubbish and the beggars. Poipet is nothing more than a big shanty town and I would really not recommend staying there for any length of time. Get to Siam Reap ASAP and get out of there. It is possible to catch government busses but the last one will be some time in the afternoon so you are likely going to have to get stitched up by the tour busses to Siam Reap. What the scam is, is to basically leave as late as possible so when you arrive in Siam Reap, you are taken to a guest house and will likely stay, as it will be too late to find somewhere else. This tactic is a tried and tested method and I couldn't be bothered finding anywhere else. In actual fact the scammer caught the bus and was coming out with all sorts of bull 5hit about Siam Reap being really dangerous at night etc. He also had 6 fingers and kept insisting on shaking my hand.
Once you have bought a ticket to Siam Reap, you will probably have to wait at the bus station/agents office for a while before leaving. The road from Poipet to Siam Reap is probably one of the worst in SE Asia , but you may well find it so bad that it is funny. I found it hilarious it was so bad, and to be honest with you it was a laugh. Imagine hammering down this dirt track in this 5hitty bus full of backpackers. Dirt is flying in through the window and everything has dust on it, you have stopped wiping dirt off as you have accepted this will not help. The road is basically just craters, so every other second you are flung up into the air out of your seat. You go past other busses full of travelers that have broken down that could well be part of the scam. This scenario really could not get any more surreal. Then you realise it can as the bus pulls up and a monk gets on.
So if you are planning this trip aim to be over in Cambodia around lunch time. Any later and you will certainly be caught up in the scam and will not arrive in Siam Reap until 10pm or later.