BANGKOK, Sept 18 (Reuters) - Thailand’s central bank said on Monday it had taken action against what it said was “periodic speculation” in the baht as the currency hovered at more than 28-month highs against the U.S. dollar.

The central bank has resolved problems with a number of financial instiutions which had irregular transactions, Bank of Thailand Governor Veerathai Santiprabhob told reporters. He did not elaborate.

The baht’s rise was driven by Thailand’s current account surplus, investor confidence in the economy, and receding concerns over political risk, he said.

The baht traded at around 33.08 per dollar on Monday morning. It has appreciated by 8.2 percent against the dollar so far this year, making it Asia’s best-performing currency.

The central bank has forecast Southeast Asia’s second-largest economy will grow 3.5 percent this year after 3.2 percent last year. It will review that projection at its monetary polic review on Sept. 27. (Reporting by Kitiphong Thaichareon; Writing by Orathai Sriring; Editing by Eric Meijer)