Some options for diving from Khao Lak:

• The Similan Islands - Thailand's premier dive destination. Nine granite boulder islands covered with lush tropical vegetation and surrounded by turquoise water and vibrant reefs. Day trips are possible but liveaboard trips are the best way to enjoy the area.
  
  
• Richelieu Rock - The best place in Thailand to see whale sharks. Sightings are possible anytime in the November to April high season although February to April are the best months.
  
  
• Koh Bon and Koh Tachai - Two limestone islands with strong currents and good big fish encounters, especially manta rays.
  
  
• Surin National Park - Visited by liveaboard. Pristine marine life. Less visited than the Similans.
  
  
• Burma/Myanmar - Remote wilderness diving. Made famous for big shark diving. Now more appreciated for rare and exotic macro critters. Few boats dive the vast Mergui Archipelago so you'll probably be the only boat there.