The suspect wanted to use the money to buy a plane ticket back to Australia," Pol Lt Gen Sanit said.
Mr Cronin travelled from Nana to Saphan Kwai by BTS Skytrain and spent five minutes scouting areas outside the Thanachart Bank before the robbery, he added.
Pol Lt Gen Sanit told the Associated Press that Mr Cronin has been charged with robbery, which carries a punishment of up to 10 years in jail. No date has been set for his court arraignment, which he said could happen in late November or early December.