As discussed under 1 Nephi 3:29, the original text of the Book of Mormon occasionally used the historical second person singular pronoun thou or thee to refer to more than one person. All such instances have been edited to the plural pronoun ye or you. Here in Mosiah 2:11–12, the surrounding text uses the pronoun you: “but I am like as yourselves ...I say unto you that as I have been suffered to spend my days in your service”). In this particular instance, the change to you was made in the 1920 LDS edition.
For three more examples in this chapter of the plural use of thou and its editing to ye, see verses 25–26; for these three other cases, the grammatical emendation was made in the 1837 edition. For a complete list, see thou in volume 3.
Summary: Restore the biblically styled pronoun thee in Mosiah 2:11, even though the referent here is plural; the original text of the Book of Mormon occasionally used thou and thee for plural referents.