Thailand has a LOT of water!
When it rains, it really rains here. It's also nice and refreshing to have an hour or 2 of rain in the early morning, or in the late afternoon to bring some freshness to accompany the cool sea breeze. Plus without rain you don't get the superb waterfalls in the area either!
There are few here in Khanom, but they are worth the ride up the hills to go and bathe, swim and relax in. If you are unsure after your first few days here where they are, just ask, and we'll point you in the right direction.
Here's a really cool graph to explain when rain is more likely.
(P.S last year it didn't rain at all (2014), from February until May.