The Stock Exchange of Thailand index closed up 6.14 points or 0.44% to 1393.62 at midday on Wednesday.
Trading value was 18.25 billion baht, with 2.83 billion shares changed hands.
The SET50 index ended at 948.53 points, up 4.60 points, or 0.49%, with total trading value of 13.86 billion baht.
The MAI index went up 0.32 points, or 0.08%, to close at 398.94 points, with total transaction value of 435.86 million baht.
Leading trade by value were: BBL (+1.10%), SCB (+1.89%), IVL (unchanged), KBANK (+1.67%) and CPF (unchanged).