At least 14 protesters, three police officers and a soldier were wounded in the clashes, the first such confrontation since thousands of red shirts descended on the city a month ago.
Security force sympathy
Most soldiers and police pulled back from the site after failing to stop the red shirts, who want the government dissolved and early elections called. Some security personnel were seen throwing down their shields and riot gear and shaking hands with the protesters.
"There has been suspicion for sometime that should confrontation develop - as we have seen today - that there would be a large proportion of the military that may well side with the red shirts," Al Jazeera's Wayne Hay, reporting from outside the TV station, said.
"The military and police personnel that are present in Bangkok do not actually come from Bangkok. They also come from other parts of Thailand - the northeast, for example, which is where a lot of the red shirts' support comes from.
"So it all is almost inevitable that there will be some sympathy from within those security forces with the red shirts; after all Thailand is a deeply divided country politically."
Although the opposition-run channel was back on air on Friday, the government remained in control of the signal.
"We are still controlling any news reporting that distorts facts," Panitan Wattanayagorn, a government spokesman, told The Associated Press news agency.
Thaicom, which relays the People's Channel signal via satellite, was founded by Thaksin Shinawatra, the ousted former prime minister that many of the red shirts support, but he no longer owns it.
The clashes fuelled speculation that authorities were planning to crack down on the red shirts camped in Bangkok's historic heart and its main commercial district.
|A large security presence remains in Bangkok as the red shirts promise bigger protests [AFP]
"Journalists have been asked to leave the main area where they have been covering this protest from," Al Jazeera's Aela Callan, reporting from Bangkok, said.
"Several of the shopping malls that ventured to open their doors today have asked staff to leave because of an impending military crackdown.
"We've heard these rumours before and protesters have been asked [by their leaders] to stand firm; not to go anywhere.
"The country will be closely observing how [the prime minister] handles this situation, considering that he is facing mounting critics and is starting to look very weak in the eyes of the Thai public if he does not put a stop to the demonstrations," Callan said.
"But the government does not want to be seen as firing the first shot."
Abhisit Vejjajiva, the Thai prime minister, said on Thursday that arrest warrants have been issued for some protest leaders.
However, he also stated he would not order a crackdown, leading to criticism from some sides that he was showing weakness in handling the protests which have now lasted for almost four weeks.
A large security presence remains in Bangkok, and according to an army spokesman, about 33,000 extra police and soldiers have been mobilised in and around the capital.