A lone gunman, his face concealed behind a full-size helmet, robbed a branch of Government Housing Bank in Phuket on Friday morning and made off with Bt26,900.
Thalang police responded at 9.05am and learned that the robber arrived on a motorcycle, walked inside and drew a gun to force counter staff to fill his black bag with cash.
Queuing customers sprinted for the exit and a security guard who tried to stop the robber was instead taken hostage.
The guard was released unharmed as the robber fled on his motorcycle.
It was all over in about six minutes, police were told as they began examining CCTV recordings.