Ubuntu is available in Cambodia from Tropical Ice Cube. Many other distributions are also available.
There is a Linux User Group mailing list on Google Groups, with links to some other related groups in Cambodia.
Ubuntu and other major Linux distributions support Khmer Unicode. Khmer language support and applications are available for both Windows and Linux from KhmerOS
If you would like to join or contact me, please email me at firstname.lastname@example.org. I'd also like to hear from anyone translating software or educational material, or working with ICT in Education or Development, particularly Open Content and Free/Libre Open Source Software