Yachts must generally anchor well offshore because of shallow water which surrounds many of the islands in Phang Nga Bay. At the Paradise Koh Yao Resort, there is a channel and dock which allow a dinghy landing on any tide.
BA 3941: Similan Islands to Ko Lanta
Tides Table Phuket
See and download on www.charter-yacht.com the actual Phuket Tide Tables