A lone gunman held up a guard delivering money to ATMs outside a Kasikornbank branch in Bangkok's Prawet district shortly before 4pm on Friday.
A witness said the man was waiting when the cash-delivery vehicle arrived at the branch in Chalerm Prakiat Soi 7, just off Si Nakarin Road.
He held up the guard with a gun and made off with four boxes of cash totalling about 1 million baht, a witness said, adding that the gunman seemed to know what time the delivery would be made.
The robber fled on a motorcycle. The witness said the robbery took less than two minutes.
Police were called to scene but arrived too late.