King fired the round of the tournament to make up a 10 shot deficit and force a tie with Vandersluis on the third and final day of the event.
After five birdies on a very challenging Royal Perth championship layout saw him post a 1-under 71 in regulation, a rock solid par on the first playoff hole was enough to take the title.
It was a big day for the host nation with the Australia B team, of which King was a member, also coming from behind to snatch victory from Australia A in the national teams event.
New Zealand, leaders after round one and joint leaders with Australia A after the second round, finished in third spot.
More than 65 players from eight countries participated in the championship, an annual event held in a rotating list of countries.
The victorious Australian B team consisted of King, Paul Maslen and Chris Coats while the A team included Vandersluis, Stefan Albinski and Denis Dale.2011 Asia Pacific Senior Amateur Championship Final Results