Description of problem:
The font package should have one fontconfig config file in the package at least to let fontconfig know which alias the font is close to, which language the font is supposed to be used for etc.
Version-Release number of selected component (if applicable):
See http://fedoraproject.org/wiki/Fontconfig_packaging_tips for what kind of rules you need to add.
I am afraid I don't know Khmer script at all, so I can't give fontconfig hints. Unless Debian of other distro wrote it already or someone else is willing to write it, or help me to write, I am afraid I can't help in here.
No worries. I can help you to improve this. I'll attach one later.
Created attachment 413940 [details]
proposed fontconfig config file
Fixed in khmeros-fonts-5.0-10.fc14