Police summoned three security officers late yesterday |who had guarded a money truck when it was robbed on Friday evening - to provide more information.
Investigators also inspected security camera footage of the suspects and the routes they took prior to and after the robbery, an informed source said.
Two robbers targeted the Kasikornbank truck at the Tesco Lotus Rama I branch and made off with Bt8.45 million.
As the security guards carried the moneybags into the Kasikorn Bank branch at the building, the robbers handcuffed the sole armed guard and fled with the money on a motorcycle.
Pathumwan Police superintendent Colonel Jarut Saruttayaporn said police needed at least two days to catch the thieves.
Metropolitan Police deputy commissioner Maj-General Chanthawit Ramasut said investigators believed the robbery involved an insider.
He said police were looking into the fact that a regular guard assigned to that team was on |leave and had been replaced. Police investigators will be meeting to discuss the case tomorrow morning.