The index gained 0.03 points to 1,643.43 points, extending the 19-year high, on turnover of Bt57.45 billion.
The market was in the positive territory though Asia Pacific bourses ended lower. The MSCI Asia Pacific Index slid 0.2 per cent to 144.09 as of 4.10 pm in Hong Kong after gaining as much as 0.1 per cent.