It is narrated from Sayyiduna Ali bin Abi Talib (may Allah be pleased with him) that the Noble Prophet (peace and blessings be upon him) used to wear his ring on his right blessed hand.
Hadith Referenceشمائل ترمذي / باب ما جاء فى أن النبى صلى الله عليه وسلم كان يتختم فى يمينه / 94