Open Khmer School is one of the Khmer typefaces initiated by Open Insitute, with the support from RTI (Research Triangle Institute), for producing handwriting books for children. It is friendly, readable, and legible.
If you are looking for the highlight fonts, please find them here. I might not be able to offer much support or update on these fonts, but they are still working.
The Highlight fonts were built using the Lemon and other legacy fonts encoding. So please use the English keyboard layout to type it.