Wyn Davies (welsh-born Canadian) runs Lanta Sailing through the winter (high) season on Ko Lanta.  He has a 32' yacht called La Pinnele with local engineer Boa.  If you want something quieter and more personalised than the tour speed boats, Wyn does private tours for up to 4 people around the local islands.  He's totally flexible about numbers of days and can incorporate diving as well.  See www.lantasailing.com or contact Wyn on +66 (0)848 418 270 0r +66 (0) 862 765 371.