Turnover was rather thin, though, at Bt27.78 billion.
The index has been advancing since February 27, when the index was closed at 1,318.05 points.
Foreigners just made a comeback on Monday. In the first four days of this week, foreign net buys reached Bt5.66 billion.
Year to date, foreigners still remained net sellers, with their combined sale exceeding net purchases by Bt29.38 billion.
Asia Plus Securities commented that political tensions have declined, following the end of protests at several rally sites as well as initiatives to kick off political dialogues.
It also noted that the market will get a boost next week if the Bank of Thailand lowers the policy rate by 25 basis points to 2 per cent as expected.