Going to Siem Reap:

In Bangkok, go to the Mochit 2 bus station towards the airport. Air conditioned buses leave every hour towards Aranyapathet-Poipet (170 bahts - 4 hours). From there a tuk-tuk will take you to the border for 50 bahts. Then cross the border on foot. Watch out for picpockets! There are lots! For those who don’t have a visa there is a cashier that does them in a few minutes for 1000 bahts. Avoid intermediaries! Once in Poipet, near roundabout, pick-ups leave for Siem Reap but are obliged to stop in Sisophon bus station. Buy a seat for Battambang with one, the pick up will leave when it will be completly overcrowded and not before, once in Sisophon they will drop you to a taxi leaving for Battambang. There is numerous guest houses ther along the river. Battambang is a pretty colonial town alongside a river, spend the night there and in the morning at 7am take the fast boat ($15) to Siem Reap, you will reach the city of temples 3 to 5 hours later depending on the boat.

The journey is superb specially before arriving on the Tonle Sap lake.

Leaving Siem Reap:

Boat are leaving dayly to Battambang at 7am, as the ferry dock is located 12km south of Siem Reap town, you will have to leave the town at least one hour before