How to make Khmer font from the new file?

Dear all,
I try to make a Khmer (also known as Cambodian) font from a new file, but it’s not work.
How can I make it to work?
There are some Khmer font on the web, but I don’t want to use/follow their draft,
Thank you !!

Making a Khmer font may be difficult. It is beyond my experience. Probably it will need to have several OpenType tables. If you examine an existing Khmer font in FontCreator 7.5 or later you will be able to examine the code that is used to create the OpenType features.

I have added several Glyph Substitution (GSUB) features to my own free fonts, but I think Khmer may also need Glyph Positioning (GPOS) features.

Which version of FontCreator do you have?