The main English-language reference consulted for this branch names no developed proto-language reconstruction, only listing Khasic and Palaungic as its two constituent groups.
What would resolve this A specialist source (Sidwell 2011/2018 or a dedicated Austroasiatic comparative study) giving the state of Proto-Khasi-Palaungic reconstruction.
Openhistorical linguisticsWikipedia: Khasi-Palaungic Languages