Turnover was Bt51 billion today. The index was last seen above 1,600 points in May, 2013.
The index has advanced for four consecutive days. In the first three days of this month, foreigners were net buyers of Thai shares with net purchases of Bt4.24 billion. Its net sells year to date have narrowed to Bt20.6 billion.
Other Asian stocks were broadly higher today as investors welcomed strong US manufacturing data while Hong Kong tacked on more than two per cent following a positive reading on China's services sector.
The dollar held above the 105 yen mark after breaking it Tuesday for the first time since January, sparking a rally in Japanese exporters.
Tokyo rose 0.38 per cent, or 59.75 points, to 15,728.35 while Hong Kong jumped 2.30 per cent, or 568.93 points, to 25,317.95 and Shanghai rose 1.00 per cent, or 22.58 points, to 2,288.63.
Seoul ended flat, dipping 0.38 points to 2,051.20 and Sydney was also a touch lower, easing 2.4 points to 5,656.10.
Data showed Australian economic growth slowed in the three months to June owing to a sharp fall in exports.
Traders cheered a report from the Institute for Supply Management, which said Tuesday that a gauge of activity in the US manufacturing sector picked up pace in August, hitting its best level since August 2011.
"The parade of solid data continues," a Societe Generale analyst told Dow Jones Newswires. The figures are the latest suggesting the US economy is well on track to recovery and will add to pressure on the Federal Reserve to raise interest rates earlier than its timetable of next year.
The strong data "should keep upward pressure on the dollar, which will, in turn, make Japan stocks attractive", said SMBC Nikko Securities general manager of equities Hiroichi Nishi.