The Stock Exchange of Thailand main index fell 0.49%, or 6.94 points, to 1,418.38 on Friday.
Total trading value was 45.57 billion baht, with 9 billion shares changed hands.
SET50 index dropped 0.42%, or 3.90 points, to 919.63 in trade worth 25.82 billion baht.
MAI slipped 0.38%, or 2.29 points, to 598.85, in total transaction value of 1.81 billion baht.