Change Thai Keyboard Mapping: El Capitan

I would like to change the layout of the Thai keyboard, or create a new one with a different key mapping.

This old article describes a means but it may not apply to El Capitan: http://xahlee.info/kbd/osx_keybinding.html.

The "KeyBindings" directory does not exist in El Capitan; but:

/Library/Keyboard Layouts

~/Library/Keyboard Layouts

do exist, however, they are empty, despite having two Thai layouts (so I would expect to see a binding file).

Thank You.

Macbook Pro 2012 / OS X El Capitan 19.11.6.