Banking shares gained 1.7 percent, outperforming the broader SET index, amid good buying interest from domestic institutions for retirement mutual funds (RMFs) and long term equity funds (LTFs), brokers said.
The SET index was up 0.5 percent at the midday break of 0530 GMT.
Siam Commercial Bank, the most actively traded, rose 3.8 percent to 177.5 baht, climbing at one point to a 16-year high of 178 baht. About 8.6 million shares changed hands, 1.5 times the average full-day volume in the last 30 sessions.
Siam Commercial Bank and other major banks such as Bangkok Bank Pcl and Kasikornbank Pcl were among blue chip stocks that were targets for RMFs and LTFs, Tisco Securities said in a note to clients.
The funds offer tax breaks and generally see high demand toward the end of the year.
Reporting by Viparat Jantraprap in Bangkok; Editing by Anupama Dwivedi