The baht plunged to its weakest level since September 2009 amid sustained outflows from local assets and a selloff in Chinese equities.
Global funds have withdrawn a net US$199 million from stocks and bonds this month, taking total outflows for 2015 to $1.2 billion, data compiled by Bloomberg show.
The benchmark SET Index of local shares fell 0.5% on Wednesday after dropping to an almost seven-month low Monday as investors grapple with potential risks stemming from Greece's likely exit from the euro and a stock rout in China.
The baht declined for a third day, retreating 0.2% to 34.007 a dollar as of 11:49am in Bangkok, according to data compiled by Bloomberg. The currency, which has lost 4.3% in the past three months in Asia's second-worst performance, sank as low as 34.055 earlier. A gauge of dollar strength rose for a fourth day.
"Foreign outflows signal a weaker outlook for the baht," said Thanomsri Fongarunrung, an economist at Phatra Securities in Bangkok. "The ongoing anxiety in China's stock market and its economy has further weakened sentiment for the baht and other currencies in the region."
China, Asia's largest economy, is the second-biggest export market for Thailand after the US, accounting for about 11% of total overseas shipments in the January-May period, according to a commerce ministry statement dated June 26.
Sovereign bonds climbed, pushing the 10-year yield down four basis points to 2.89%, on course for its lowest close since June 3, according to data compiled by Bloomberg.