It is an unique set of numbers assigned by STTA. With immediate effect, all local participants registering for the tournaments are to include the Player ID on their registration forms.
Where to find my Player ID?
So long as you have participated in any of STTA or STTA co-organised tournaments, you will be assigned to a Player ID. Please refer to http://stta.tournamentsoftware.com/find/player, to find the Player ID.