-th/-st endings do not indicate tense or voice. There is a rumor floating around that they do (and thus indicate more information/accuracy than modern English), but this is wrong. It is simply a matter of -st being second-person singular, and -th being third-person singular. E.g. "I love"/"I have" (first person singular), "thou lovest"/"thou hast" (second person singular), "he loveth"/"he hath" (third person singular).