To get the crystal waters you are talking about, you may look get off of Phuket to other beaches.

There are some quite nearby, like Koh Ratcha or Coconut Island. If you like the backpacker scene, PhiPhi may be your thing... it's not mine!

Naiharn beach is one of the nicest in Phuket.

But, listen to the warnings about the strong deadly rip tides that take many lives each year, despite the warnings. Simply put, beaches facing the open Andaman Sea are subject to strong seas. Choosing a sheltered beach isn't that hard to find, just take note of the geography.

You will have tons of Russians and Chinese if you pick mainstream spots, even in May.