American Justin Thomas shot a 67 to reach 18 under .
American Justin Thomas lead by two shots from red - hot world No. 6 Hideki Matsuyama , who has won four of his past five tournaments .
American Justin Thomas shot a 67 to reach 18 under and lead by two shots from red - hot world No. 6 Hideki Matsuyama , who has won four of his past five tournaments .