@ rajeshbp, but arent the khas and newar mallas different? as far as i know malla was a honoric title like khan or mirza or dewan so the khas lords and mallas of tirahut put malla titles when they rose to power like the shah thakuris.also when these terai mallas came to nepalmandal ,they rose to the power of sovereign rulers whereas the mallas of khas province were also called challas.so the ktm mallas are actually vedic high castes of north indian plains whereas the khas malla are khas aristocracy.
also, i have not seen malla,chand or shahis putting thakuri at the end of their names. saugat malla,gyanendra malla, lokendra b. chand,nir shah etc are some examples. but some thakuris just write thakuri as their surnames like suraj singh thakuri.rajesh hamal is also thakuri but i havent seen any of hamal with thakuri added to his surname.