
The baht opened at Bt34.385 to a dollar before slumping to Bt34.9598, its weakest since April 2007. It closed at Bt34.9093.
A treasury dealer said the baht depreciated in line with other currencies in the region before moving in A narrow range in the afternoon. The central bank apparently stepped into the market to stop the rapid change in the value of the currency.
"It was less volatile than other currencies such as the move of 300 points of euro, 400 points of yen and more than 300 points of pound sterling," she said.
BOT senior director Pongpen Ruengvirayudh said the baht was weaker in line with other currencies in the region because foreign investors unloaded their investments in risk assets in emerging markets.
She said there was no speculation in the forex market from exporters, importers or commercial banks.
BOT assistant governor Duangmanee Vongpradhip said the central bank had tried to let the baht move by market mechanism and be consistent with other regional currencies.
It has not yet experienced the amount of capital outflows so significantly that affected the currency, she said.