Adit Laixuthai, an executive vice president, said that the employee committed a serious crime and the bank filed the complaint on February 27.
He added that 5 customers affected by his action have filed charges with the police.
Reports go that about 200 clients were lured to buy gold funds with combined value of over Bt1 billion.
Adit added that the bank has contacted clients who may have fallen victims.
"KBank wishes to apologise to clients who have been affected by the incident. We are held responsible for the remedy. With proof of negligence, we will take responsibility of damage for all individual clients," the executive said in a statement.