I would like to recommend you to go to Koh Chang.It is a great locations to learn scuba diving in Thailand with aquarium like conditions, mostly have a great visibility! (scubadivingkohchang.com)
PADI offers different programs, whether you want to learn Scuba diving for the first time or you are already a Scuba diver wanting to continue your diving education, there is an online program for you. (akumaldiveshop.com)
Padang Bai, Nusa Penida, Nusa Lembongan will be likely the spots where to access the dive sites during your training to progressively and safely learn Scuba Diving. (twofishdivers.com)