One of the missing features in Hunspell (the program used for the Khmer spelling checker) is that when two words are incorrectly joined together it suggests the two words be split into two separate words with a space between them. This causes more work for the user as they need to then delete the space and add a zero-width space in its place. We requested a feature change in Hunspell to suggest a zero-width space between words for Khmer rather than a visible space.

Please help get this change into Hunspell by adding your support in the comments on this feature request here: Hunspell Feature Request for Khmer Spelling Checker