A Provincial Police Region 5 spokesman said the suspect, Sumek Lertphanupat, was the driver of the cash delivery van that was parked at the bank's Mae Rim branch on March 6.
Police seized about eight million baht from Mr Sumek, who allegedly confessed that he spent some of the stolen money while on the run.
The suspect told investigators that he stole the money because he was unhappy with the bank, and said he had no accomplices, according to police.
Police said they did not believe him entirely and would continue investigating.
Read the original story on the Bangkok Post here.