Phuket is one of Thailand's most developed beach resorts. That means there's a wide range of accommodations in all price categories, as well as a few more distractions once you leave the beach. But, that high level of "could-be-anywhere" development is because there are a lot of tourists to serve. Phuket is not the place to "get away from it all."
In the end, our personal favorite is the little known provincial town of Songkhla in the deep south. The beach is rather "wild", with the occasional rock outcrop, but it's natural wind-swept beauty is precisely why it appeals. Few tourists frequent this part of Thailand, yet there are many interesting sights around town as well as further afield.
Of course, there's no point in going to the beach if it's going to rain. All of Thailand is subject to the seasonal monsoon cycle, but it peaks in different destinations at different times. See our Phuket vs Samui weather chart for a simple comparison of the seasonal rainfall averages for two of the most popular destinations.