Naran Thammawaranukhup said he discovered the 51-karat necklace was missing after a group of foreigners had visited his shop, the Blue River Diamond located in the mall’s Hall of Mirror zone.

He rushed to Pathum Wan police station to report the crime.

An investigator from the station said the store’s security camera filmed a group of five Middle-Easterners – one woman and four men.

“They came in the shop separately and pretended to select items, spending around 10 minutes before leaving.

“Some of them might have asked the sales clerk to let them get a closer look at the necklace, which provided an opening for them to make off with the piece,” the officer said.

“We will select the best shot from the closed circuit camera for further investigation and arrest,” he said.