The expression “कहीं का” (literally “of/from somewhere”) is used to emphasize insults or derision.
It could be translated as “no good” or “good for nothing”, etc.
It’s often used in exclamations, and it often follows the word that it emphasizes:
नालायक कहीं का – “That unworthy, good for nothing (person)!”
चोर कहीं का – “That no good thief!”
झूठा कहीं का – “That no good liar!”