Amantha \a-man-tha, am(a)-ntha\ as a girl's name is pronounced ah-MAN-thah. Possibly variant of Amarantha, a flower name. Also a short form of Samantha.
Baby names that sound like Amantha are Amanda, Aminta and Amynta. Other similar baby names are Amalthea, Amana, Symantha, Simantha and Semantha.