Historically thrash and thresh are dialectal variants of the same original word. In current English, thresh is the expected specialized term when referring to separating grain from the husk, while otherwise thrash retains its general meaning, ‘to beat’. This is the only instance of the word thrash (or thresh) in the Book of Mormon text. (The King James Bible, on the other hand, systematically uses thresh in reference to agricultural threshing.) In the 1888 LDS edition, thrash was replaced by the standard thresh, but since that edition never served as a copytext, subsequent LDS texts have maintained the dialectal thrash. For further discussion, see the etymological information under thrash in the Oxford English Dictionary.
Since the use of thrash here is potentially confusing to modern readers, it could be replaced with the expected thresh in the standard text. The critical text, of course, will maintain the original thrash.
Summary: Maintain in Ether 10:25 the original thrash, the reading of the earliest text; in standard English, thresh is the expected word here.