Police believe the Polish suspect arrested for allegedly blowing up an ATM booth and making off with more than 300,000 baht in cash was planning similar robberies.
After examining items seized from the suspect during his arrest on Tuesday, national police chief Chakthip Chaijinda said he believed the suspect, identified as Gracjan Pavel Stanisewski, could have made another "two or three" bombs.
The items were bought in Malaysia and the investigation found the 36-year-old suspect had bought more for a new target, Pol Gen Chakthip said Wednesday.
- Earlier report: Pole blew up ATM with 'balloon bomb'
"He probably would have left Thailand permanently," if he struck again, he said.
Mr Stanisewski was found to have left Thailand for Cambodia on Sept 15, two days after the bomb blast on Sept 13 which shattered the ATM booth in front of a Tesco Lotus hypermarket branch in Soi Krungthep Kreetha 35 in Bangkok's Saphan Sung district.
He went to Cambodia, and took his Cambodian wife to Malaysia.
Mr Stanisewski was "probably preparing to escape to Malaysia" after returning to Thailand to commit a second robbery, Pol Gen Chakthip said.
However, the man was nabbed by police at an apartment on Ramkhamhaeng Soi 52 in Bangkok's Bang Kapi district on Tuesday after investigators spent nearly two weeks days hunting him.
Mr Stanisewski has denied charges of committing robbery and destroying property.
"It doesn't matter whether he denies or confesses, we have evidence to implicate him in the crime," Pol Gen Chakthip said, adding forensic police officers found his fingerprints and traces of his DNA on items found on gathered evidence.
Following the ATM blast -- the first robbery of its kind in Thailand -- investigators tracked down the suspect via footage from security cameras and found he disappeared at the end of Soi Krungthep Kreetha 15/1 over waste ground near a pond.
The discovery of two pieces of black tape near the pond prompted officers to have divers scour the pond.
The search of the pond turned up a heavy bag containing items that included white trousers, a motorcycle helmet, gloves, a loaf of bread, and 3,100 baht in cash.
Investigators discovered the brand of bread found is only sold at 7-11 stores, so traced all sales of this particular brand of loaf between Sept 9 and 13.
They eventually found a 7-11 branch, located between Soi Krungthep Kreetha 5 and 7 that had sold bread to a suspicious-looking customer on Sept 11.
A check of the store's security camera found the buyer was a heavyset foreigner wearing white trousers with a tartan pattern. The trousers are believed to be the same pair as the one found in the bag retrieved from the pond, according to investigators.
Police also used security camera footage to trace the buyer's movements after he left the 7-11 store and found he disappeared in Ramkhamhaeng Soi 50.
People in the area who were shown the man's photo told police they saw the foreign man at the apartment in Ramkhamhaneg Soi 52. It was the last piece of the puzzle that led to his arrest.
According to police, Mr Stanisewski was renting a room and living with his Cambodian wife, identified as Sukmi Ruean.
Police are not sure whether his wife was an accessory to the robbery, Pol Gen Chakthip said.
But the evidence officers have at the moment points to Mr Stanisewski having committed the crime alone, the national police chief said.
"This type of crime is very new to Thailand. It's the first time we've seen something like this," he said.
