Nice hot springs, most of the visitors go for it. Water is very hot so try it before entering. Also there are nice hiking trails and waterfalls which we enjoyed a lot especially that at the end we jumped into the springs.
Beautiful Bay that you can reach by boat from Phuket but ask in a few places before choosing a 'driver' as prices might differ... Totally worth to visit! Phang Nga reminds me of Halong Bay in Vietnam.