The baht's strength has mainly been driven by the country's hefty current account surplus, not "hot money", or speculative fund inflows, Veerathai Santiprabhob told a seminar late on Wednesday.

The baht will remain highly volatile, given external uncertainty and high global liquidity, he said.

"Nobody can tell if the baht will go higher or lower, but it's likely to be more volatile," Veerathai said.

The baht has gained 7.7% against the U.S. dollar this year, making it Asia's best performing currency, and putting further pressure on Thailand's trade-dependent economy amid global trade tensions.

Veerathai also said Thai banks' net interest margins were high -at 2.7-2.8%, double those of banks in Singapore - and should be lower.

There are no clear measures on how to reduce them yet, but the central bank may consider allowing more non-banks to compete in the market, he said.

(Reporting by Kitiphong Thaichareon and Satawasin Staporncharncai; Writing by Orathai Sriring; Editing by Kim Coghill)