The Similan Islands marine national park is a mecca for all certified divers. Great viz and stunning geology. Very few people can say that on their Open Water course they saw manta Rays and Whale sharks. Well now here is the chance.
You can get your Open Water certification on a live aboard. You you do you pool and class session during the day and head out to the Similans in the evening. Then you have the next 3, 4 or 5 days diving in one of the best locations in the world to complete the required dives.
You also have enough time and dives to go straight into the advanced course. So the Open Water in the Similan Islands and then your Advanced course at Koh Tachai and Richelieu Rock. It does not get better than that.