One of the issues with the current Khmer Unicode fonts is the English characters included do not look good (and this is understandable as they were not meant to be used as English fonts). But for some, we use both English and Khmer, in certain documents and so having a font that displays Khmer and English properly is necessary. We recently combined the KhmerOS Battambang font with Droid Serif to create an appealing sans-serif font for both English and Khmer.