Which is the best beach holiday destination in Bangkok?

What i need to know is which is the best beach around thailand. Like i said earlier, ive been to phiphi and phuket and ive heard of koh samui, krabi and chang mai. So i need to know which one is the best in terms of beach, massages, tourism (places to see) and hotels… And if there are any other ... There are some interesting and famous national parks in Chiang Mai; i.e. Doi Inthanon, Doi Suthep, Dokmai Garden, Elephant Natural Park, Hill-tribe tourism and trekking, etc. ...