Here we have two minor scribal errors in 𝓞. In the first case, Oliver Cowdery initially wrote thou shall, but then he virtually immediately overwrote the final l with a t (there is no change in the level of ink flow). As discussed under Mosiah 12:11, there has been a tendency in the textual history to replace the archaic shalt with shall.
In the second case, Oliver Cowdery started to write smites in 𝓞 instead of smite. He cut off writing before finishing the final s. However, when he came to copying this passage from 𝓞 into 𝓟, he misread his aborted s as a full s and thus wrote smites in 𝓟. Obviously, “God shall smites thee” is impossible. The 1830 compositor set the correct smite.
Summary: Maintain in Alma 30:47 the corrected reading in 𝓞: “therefore if thou shalt deny again / behold God shall smite thee”.