"Tho'" is a commonly used abbreviation for "though" in informal writing. However, there are a variety of synonyms that can be used instead of "tho'". Some options include "although", "notwithstanding", "despite this", "regardless", "even so", "in spite of", and "be that as it may". These synonyms can be used to convey a similar meaning as "tho'", indicating that there is an opposition or contrast between two ideas. By using different synonyms, writers can add variety to their writing and avoid repetition. Ultimately, choosing the appropriate synonym to replace "tho'" will depend on the context and tone of the writing.