Thailand forum

It will be high season in Samui. Each side of the south has a different low season, which is the monsoon. Phuket and Phi Phi will be at the start of it, although usually it doesn't get bad until August or even September. But given the recent weather there is no way to tell what it will be like on either side.

As for Malaria, this is usually not found in the south although there have been a few cases. Dengue Fever is what you should be worried about. There is nothing you can take to prevent this, just be sure to use your mosquitoe repellent.

I was in Thailand with my boyfriend at exactly the same time last year, and will actually be there at exactly the same time again this year (June 14th-July 26th). As guava_girl said, Phi Phi and Phuket (on the Andaman coast) will be wetter than any islands on the Gulf coast, such as Samui. My advice would be to hit Phi Phi and Phuket as early as you can, as a lot did change in one month when we were last there! So yeah, try to get to those islands as early in June as possible and expect some rain...but Samui should be nice and sunny at that time!

Also, we didn't take malaria tablets because we were advised that it's not such an issue away from border areas, and especially in the South. If you just take necessary precautions you should be fine, although I wouldn't bother with a mosquito net in Thailand (we lugged ours around for 3 months and unpacked it ONE time...waste of money!), especially if you're going for a/c rooms!