The seizure of two assault rifles from a car at a resort in Nakhon Nayok's Muang district on Friday has triggered concerns the weapons may have been intended to stir up political violence in Bangkok.
The find has prompted the army to ratchet up its vigilance against weapons which could be brought into the city to stir unrest.
The firearms were found in a white Mazda parked at the entrance of Juntra Resort while police were investigating an unrelated theft complaint filed by a customer, Nakhon Nayok deputy superintendent Chatri Promlampak said.
The resort is owned by former government MP Sitthichai Kittithanesuan. A probe found the car belongs to another politician, an adviser to a caretaker minister, the source said.
An army source said military and security authorities have not ruled out the possibility of the weapons being linked to the political unrest.
Troops attached to the Internal Security Operations Command (Isoc), who accompanied police during the weapon search, claimed high-ranking police officers and politicians had lobbied the investigation team not to confiscate the car and weapons.
The incident was reported to army chief Prayuth Chan-ocha, who later gave an order not to allow the rifles to be released as the case concerns security.
The discovery also prompted Gen Prayuth to order his subordinates in the army and the Isoc to beef up vigilance against people carrying weapons.
The army was also notified that numerous weapons are being kept in the house of another politician in the province. "Gen Prayuth has praised Nakhon Nayok police for adhering to the laws and ordered the Isoc to follow up the investigation," the source said.
Meanwhile, Democrat Party spokesman Chanvanond Intarakomalyasut said the car which carried the weapons belongs to a high-profile politician in a Central Plains province. He urged authorities to pursue the question of whether the arms were intended to cause mischief in Bangkok. Police should note the fact the weapons were found in Nakhon Nayok in a car registered in Chiang Rai.