I have to say my best holiday was on Koh Tao in Thailand. Beautiful lush green jungle with a few mountains and absolutely amazing views. It is for sure worth a visit. I did my Open water course there and had a lot of fun. You can choose from many languages and diving centers. i got all my information from a site called Kohtao.asia.
a very nice site that explaines the island and gives you an overview about everything. Look at the picture i posted so beautiful i really wanna go back.

happy travel

Stony