Chalong Police Chief Investigator Lt Col Tachin Deethongon said he was notified of the robbery at 1pm.
Official reports give the time of the robbery as 12:55pm, but CCTV recorded the man exiting the bank and leaving the car park at the mall at 12:46pm.
The man, described as Thai, wearing black cap, grey v-neck T-shirt and three-quarter shorts, entered the bank and calmly threatened bank staff with a revolver.
Frightened, staff at Counter 3 handed over B137,000, and staff at Counter 2 handed over B23,000.
The man was last seen on a red Honda Wave motorcycle heading along Wiset Rd before turning into Soi Suksan 1.
Police are continuing their search for the man.