I am planning to go for Koh Similan/Koh Bon/Richelieu Rock liveaboard during Apr 4th weekend taking advantage of the Good Friday holiday..
I contacted few dive companies in Khao Lak and found SeaDragon Divers to be one of the cheaper and reliable ones with good rating..
It will cost a decent amount ( Protected content ) for 4D/4N liveabord with 13 dives and all food included.. Seems like a lot but I figured its worth it since this is one of the best sites in the world!!
I am flying into Phuket on 4th evening (Wed) with Tiger Airways and plan to take a bus to Khao Lak since the boat leaves on 4th night, It returns to Khao Lak on 8th evening and I fly back the next day with Tiger as well..
April is one of the best times to see whale sharks/manta rays/hammerheads in Thailand and its going to be insanely awesome!!
Let me know if anyone's interested out there and I can hook you up with the dive center..