Hi Doro,
All the problems people have mentioned about crowds and tropical beaches and awesome limestone are true. It's hell out there.
I've been to Krabi 3 times and have not experienced any problems related to the insurgency in the south. That is (obviously) not a guarantee of anything, but Thais in general are lovely people and literally thousands* of foreigners go to the Rai Lay peninsula every month.
It's really hot. There's lots of other tourists. You will probably love it.