"PDRC key figures and their members joining the protest should immediately end or reconsider the blockade of the television stations," the Thai Journalists Association and the Thai Broadcast Journalists Association said in a statement on Friday.
The campaign is aimed at the five free mainstream channels: 3, 5, 7, 9 and 11.
By demanding that the stations carry only news related to its campaign, the People's Democratic Reform Committee is threatening the rights and freedom of journalists to perform their duty, it added.
The protesters must end their pressure on the media to engage in one-sided reporting and respect editors' decisions about what to broadcast to the public, it said.
Friday's intimidation campaign is the second by the PDRC, which also threatened to shut down broadcasters that failed to carry its "news" during the Bangkok Shutdown campaign.
That threat too was roundly condemnet and PDRC leader Suthep Thaugsuban later apologised.