Pol Lt Col Somchai Thongsa-ngiam, a deputy inspector at Muang Ratchaburi police station, said on Monday that the vehicle belongs to Jirathon Jakrawat, aged 42.
Ms Jirathon said she parked her pickup truck outside the Democrat office on Sunday morning and travelled to Bangkok to join the anti-government protest led by the People's Democratic Reform Committee (PDRC). She went with a group of friends and former Democrat MP Boonmak Sirinaowakul.
When she returned to Ratchaburi around midnight she found several bullet holes in the body of her pickup truck and decided to call the police.
"I suspect that the shooting is politically motivated because I've been taking part in the PDRC rallies since the beginning and I usually park my pickup truck here," said the anti-government protester.
"I think the shooter might think that the vehicle belongs to Mr Boonmak (who is also core member of the PDRC)."
Police were investigating.