This is the bizarre moment shop assistants stayed perfectly calm while a gun-wielding robber stole gold jewellery from their store.

The burglar was seen wearing a long-sleeved jacket and a full-face helmet as he approached the Saengmanee Thong Shop in Nakhon Ratchasima, northeast Thailand, on July 27.

CCTV footage shows the gunman pointing his pistol at the clerks, who barely flinched as he ordered them to fill a small plastic bag with valuable accessories.

One attendant calmly opens the glass display case and retrieves a bunch of golden necklaces while her two other companions stood by staring at the man's firearm.

A top-view video of the incident shows an employee in white fidgeting with her phone before hiding behind a door upon seeing the man pull his gun.

When the thief turns and leaves with his loot, the shop assistants belatedly crouched down the checked to see if the intruder had left before grabbing their phones to call for help.

The suspect reportedly made off with five gold necklaces worth a total of 150,000 Baht (about 4,160 USD).

Nakhon Ratchasima police said they have two suspects now in custody who match the thief's appearance and gait with a limp on his left leg. Further investigation is currently underway, they added.