Circuit breaker triggered on SET index

The Stock Exchange of Thailand circuit breaker is triggered as the index falls 10% on Thursday afternoon trading. (Bangkok Post file photo)

A trading circuit breaker was triggered as Thailand’s stock market fell by 10% when the afternoon session resumed on Thursday, only the fourth time it has been used to curb excessive volatility.

The Stock Exchange of Thailand (SET) index fell by 125.05 points to 1,124.84 points in turnover worth 61.3 billion baht.

Trading was halted from 2.38pm to 3.08pm. The pre-open trading period is set at 2.58pm, according to the SET.

The SET circuit breaker has been activated only three times in the past to handle high-volatility trading.

The first was in 2006 when the Bank of Thailand temporarily imposed capital controls. The second and third times were on Oct 10 and 27 during the 2008 subprime crisis.

There are two stages for a circuit breaker. The first occurs if the SET index falls by 10% from the previous day's close. All trading in listed securities is halted for 30 minutes.

The second stage occurs if the index falls by 20%, or another 10%, from the previous day's close. Trading in all listed securities is halted for one hour.