The composite index gained 22.20 points or 1.41 per cent to 1,601.15 points, on turnover of Bt48 billion.
The previous 19-year high was registered in March, at 1,598.13.
Tokyo also soared to its highest close in almost five years.
Concurrently, US stocks also opened higher Tuesday in the wake of solid corporate earnings reports and stronger overseas markets.
Five minutes into trade, the Dow Jones Industrial Average rose 32.55 (0.22 per cent) to 15,001.44.