Police arrest Vorapoj Buaphet, 35, yesterday.

The two men stole gold necklaces from the Carrefour department store at Ratchada and fled in a taxi to Ratchadapisek subway station, where security guards tried to obstruct them.

One of the gun-toting robbers, Vorapoj Buaphet, 35, held the woman guard, Saowanit Kaewdeang, 31, hostage and forced her to hide in Soi Ratchada 22 - while watched by onlookers.

The robber refused to negotiate with police officers but approached a pickup truck driven by an observer. He forced the driver to get out of the car then drove it towards Ratch-ayodhin, still holding Saowanit.

Bang Khen traffic police finally stopped the vehicle at a roundabout and charged the man. But the guard had been freed by then, and got away with just minor injuries.

Saowanit said the robber had his gun trained on her while driving the pickup with his other hand. He had hit her on the head with the gun and accidentally scratched her face with his knife.

Vorapoj confessed to police that he and a friend stole three gold necklaces from a man in front of a men's toilet in the department store, after hitting him on the head with a gun. He said he wanted money to repay a debt and had robbed other people previously.

Vorapoj, who carried a .38 gun and a pocket-knife, was charged with robbery, illegal detention and illegal possession of weapons. The gold necklaces were allegedly taken by his accomplice, Isara Panto, 47.

The man they robbed, Chaiwit Nareemont, 45, needed to get 20 stitches after being hit on the head six times with the gun.

According to subway executives, a closed-circuit-TV camera at the station recorded the robbers' faces. The second thief Isara reportedly took the stolen necklaces on a train bound for Bang Sue station.

Subway bosses believed the incident would not affect subway operations because people who behave unusually are usually spotted via surveillance cameras. There are totally 700 CCTV cameras covering up to 95 per cent of subway station areas.