Annop Khongsaengkham, 30, was caught in front of an apartment building in soi Naksuwan of Yannawa district on Thursday.
Lumpini police investigation chief Thanes Meethong said the arrest followed a complaint by an American that he was robbed of 3,000 baht by a taxi driver armed with a gun on Sukhumvit Soi 15 of Khlong Ton Nua in Wattana district late on Tuesday night.
The driver then asked the passenger to get out of the cab.
Police examined footage of closed-circuit television cameras in the area to find clues to arrest the suspect, said Pol Lt Col Thanes.
Mr Annop allegedly confessed to another hold-up.