How to have Khmer unicode keyboard in Mac

After you downloaded the file then copy file to HardDisk > Library > KeyboardLayout. 

That is how to install Khmer Unicode for Mac OSX
 

Next step is to Add Keyboard Layout
 

Go to System Preferences > Keyboard > Input Sources to add Khmer Unicode Keyboard Layout

https://www.rean.me/2017/06/khmer-unicode-mac-osx-apple.html