How to choose between Thailand's classic islands

With hundreds of dreamy tropical islands scattered along Thailand’s extensive coastline, choosing your ideal island escape can be overwhelming. Each one of those specks in the ocean is a tantalising composition of turquoise water, lush inland jungle and divine beaches - so how's a traveller to choose? First-timers often start with Ko Samui, Ko Pha-Ngan and Ko Tao, a chain of three popular islands along the gulf coast.