As discussed under Mosiah 12:11, there are a number of cases in the history of the text where an original shalt was replaced by shall. Here in Helaman 10:5, the 1837 edition accidentally changed thou shalt to thou shall. This nonstandard usage was retained in the first three British editions, but the correct thou shalt was restored in the 1840 edition and in the 1879 LDS edition. The critical text will maintain thou shalt. There were a few instances in the earliest text of thou shall, as explained under Mosiah 12:11.
Summary: Maintain the original instance of thou shalt in Helaman 10:5, the reading of the earliest textual sources.