The first instance of shalt in this passage was changed to shall in the 1840 edition. Since the second shalt was left unaltered, we can assume that the change to shall was accidental. The subsequent 1858 Wright edition restored the correct shalt. As discussed under Mosiah 12:11, the earliest text has a few instances of thou shall rather than thou shalt.
Summary: Maintain in Helaman 7:24 the two instances of thou shalt, the reading of the earliest extant text for this passage.