I second that esp. the 'ride of your life' bit.
http://www.talesofasia.com/ for more instructions. I stayed at Gordon's guesthouse (the guy who runs this website) US$14, very nice and clean and comfy, A/C, bathroom. Thought it was luxury.
Alternatively, can fly to Phnom Penh from Bangkok or KL (AirAsia flying there next month). THen go to Siem Reap by bus for US$4, very fast and comfortable road and buses. Then come back to thailand by road, that way you only take that 'ride of your life' once!