Red-shirt leader Jatuporn Promphan on Thursday asked police to lay more than 200 criminal charges following social media attacks on him in the run-up to last month's local elections.
The chairman of the United Front for Democracy against Dictatorship (UDD) went to the Technology Crime Suppression Division (TCSD) and asked that the charges be filed against those who had either posted false information about him or shared it online.
The legal action stemmed from his open support for Boonlert Buranupakorn, a candidate in the Provincial Administrative Organisation (PAO) election in Chiang Mai during the campaign for the poll.
Mr Boonlert, who previously served as PAO chairman in Chiang Mai, was defeated by Pichai Lertpongadisorn, a former senator, who was backed by the Pheu Thai Party and former premier Thaksin Shinawatra.
Mr Jatuporn was criticised by many Pheu Thai supporters for betraying the cause of the red-shirt movement, which has been closely allied with the main opposition party.
Before the PAO elections on Dec 20, Mr Jatuporn said Pheu Thai had falsely accused Mr Boonlert of tending to side with the ruling Palang Pracharath Party and that a leading figure in the party had been allowed to unfairly pick Mr Pichai over Mr Boonlert.
Mr Jatuporn said that throughout several months of PAO campaigning, he had been bombarded with malicious comments and disinformation in the social media.
He warned those responsible of the severity of committing a cybercrime by making and passing on unfounded allegations but the attacks against him did not relent.
Accompanied by his lawyer, he on Thursday sought to have charges filed related to more than 200 incidents. Some people, including activists, would face more than 10 charges each.
Mr Jatuporn vowed to next week seek similar charges against more people including politicians and lawyers, if they did not stop directing untrue allegations against him.
In one case, he said, a person falsely quoted him as saying: "Prime Minister Prayut Chan-o-cha is a statesman, unlike Thaksin who fled the country." The UDD chairman said he had checked with the website from which the quote was allegedly taken and it denied it ever ran such a quote.
Mr Jatuporn added he had also been accused in online messages of switching sides in a bid to serve the interest of the military.
He insisted the UDD's mission to fight against elitism had not been won but the torch had been passed to the young people, a reference to the youth-led, anti-government protesters under the Free Youth umbrella.