Thailand's benchmark SET index fell more than 2 percent, underperforming other Southeast Asian stock markets, as strength in the Thai baht kept the market cautious over possible measures to stem the currency's rise, brokers said.
The SET index was down 2.02 percent at 1,536.53 by 0349 GMT, sliding at one point to 1,534.27, the lowest since March 4.
It dropped 1.5 percent on Tuesday as the market was concerned policy makers might implement measures to stem the current influx of capital and halt the baht's continued appreciation, said broker Krungsri Securities in a report.
"More downside could be in store for Thai stocks today if external situation remains worrisome or there are new measures that could hurt market sentiment," strategist Teerada Charnyingyong of Phillip Securities wrote in a research report.
The baht was at 29.16 per dollar in early trade, the highest since 1997. Finance Minister Kittirat Na Ranong said early on Wednesday that he had no plans for measures to curb the strength in the Thai currency.
The stock market saw broad-based selling, led by a 1.8 percent drop in banking shares and a 1 percent loss in energy shares.
Technically, if the SET index fails to bounce above a five-day moving average line of 1,580, the outlook remains subdued, broker Phillip Securities said.
Reporting by Viparat Jantraprap in Bangkok; Editing by Anupama Dwivedi