The man, whose name was given as Eric Robert, 33, fired the handgun as he drove a Honda Jazz from Rawai in southern Phuket to Chalong Circle about 5am on Saturday, officers said.
He was stopped by police at Chalong Circle following the reports from residents. A search of the car uncovered a .38 handgun and 49 bullets, officers said.
The American admitted that he rented the legally-registered gun from a Thai man for 60,000 baht but denied firing it into the air.
Chalong police took the man to court on Saturday and took him to Phuket Provincial Court in Phuket City for a second interview today.
The handgun has been sent to be examined by forensics experts in Bangkok to determine whether it had been fired recently.
The American, who has a job on a ship and an Indonesian wife, has been charged with carrying a weapon in a public area and with firing it in public.