For those planning on attending the Post-Do, here is the Visa on Arrival info:
You may obtain your visa upon arrival at the two airports in Cambodia: Siem Reap and Phnom Penh and other border checkpoints
What do I need to get my visa in Cambodia (upon arrival)?
A2. REQUIREMENTS
Application for a tourist visa requires:
* A completed visa application form
http://embassyofcambodia.org/VISA_FORM.pdf
* A Passport with at least 6 months validity
* One recent photograph (2 inches x 2 inches)
* Appropriate visa fee (US$35)