The army, which recently had a well publicised spat with the yellow shirt affiliated newspaper, hastily denied any involvement in the attack.
An unknown gunman fired a shot at each of the four cars, which were parked in front of ASTV headquarters near Santi Chaiprakan Park on Phra Arthit Road. No one was hurt.
Security guard Rungrote Khaoprasert, 34, told police the four cars were parked on the street because the car park inside the ASTV compound was full.
While walking to the bathroom at about 3.25am, he said he heard four gunshots, but did not think they were nearby.
When reporters came to take the vehicles out on assignment the next morning, they noticed the bullet holes, Mr Rungrote said.
Police believe the bullets were fired from a .22-calibre handgun.
The shooting took place just two weeks after a war of words broke out between ASTV Manager and army chief Gen Prayuth Chan-ocha.
The newspaper criticised Gen Prayuth over his perceived failure to stand up for the country's interests in the Preah Vihear temple dispute with Cambodia. It also criticised his strategy in the deep South.
Gen Prayuth responded by calling ASTV Manager a "lousy newspaper".
The paper then likened the general to "a woman on her period".
Soldiers rallied in front of the newspaper offices on Jan 11 and 12 to voice their anger over the media outlet's criticism of the army chief.
Gen Prayuth, however, ordered them to back off and apologised to the public for being "moody".
Army deputy spokesman Col Winthai Suwaree yesterday said the army had nothing to do with the shooting.
Pol Lt Gen Kamronwit Thoopkrachang, the Metropolitan Police Bureau chief, said officers were investigating the case and would have to discuss possible motives with ASTV management.
Police recovered closed-circuit TV footage and noted a suspicious man in a black shirt walking on the footpath opposite ASTV headquarters at 3.25am.
At 3.26am the footage showed a picture of a car with a shot out mirror, and at 3.28am, it showed the same man walking back, heading to nearby Soi Kai Jae, which connects to several nearby roads.
A mirror on the second floor of the Anurak building, which houses the media company's administrative offices, was also damaged in the shooting.
Police will also examine footage from other nearby CCTV cameras to identify the shooter, Pol Lt Gen Kamronwit said.
The ASTV media group, which owns the ASTV Manager newspaper and a satellite television channel, is a staunch critic of the government and Prime Minister Yingluck Shinawatra's brother Thaksin.
ASTV was founded by Sondhi Limthongkul, one of the core leaders of the yellow-shirt People's Alliance for Democracy (PAD).
Mr Sondhi was wounded in an assassination attempt in 2009 when gunmen fired more than 100 M16 and AK-47 assault rifle rounds at his car.
Police and soldiers both came under suspicion for the attack but the assailants were never apprehended.
PAD spokesman and ASTV Manager columnist Parnthep Pourpongpan said he believed yesterday's shooting was intended as a threat, as the gunman had attacked at night with no apparent intention of injuring anyone.
"We have been targeted several times in the past, but the incident was the first during the tenure of the current government," he said.
Democrat Party leader Abhisit Vejjajiva yesterday urged police to track down the gunman quickly.
He said the incident represented a threat to the media, and police had a responsibility to bring the shooter to justice.
The Thai Journalists Association and the Thai Broadcast Journalists Association yesterday issued a joint statement condemning the shooting as "a flagrant act of intimidation against the media's freedom to perform their duty".
The associations said that if anyone feels that media organisations have failed to perform their duty properly, they should seek legal action rather than resort to violence.
The associations called on the national police chief to step up efforts to apprehend the shooter and to keep the public informed of the investigation process.