Is there a direct flight from Singapore to Sanya

Well, there is no direct flight between these two places. You need to transfer the flight at Haikou first. Generally speaking, only on Monday,Wednesday and Friday, on flight operates this route (Tiger Airways). For the exact info, I suggest you consult the airline.

After arriving at Haikou Meilan Airport, walk northwest around 765 yards and get to Meilan Railway Station. There are many high-speed trains that can take you to the destination directly.