0322 GMT January 17, 2021
It will be the first time such charges have been brought under so-called lese majeste laws relating to insults to the royal family in more than two years, according to Reuters.
They can carry up to 15 years in prison.
Protests that began in July against Prime Minister Prayuth Chan-ocha have increasingly turned to demands to curb the powers of King Maha Vajiralongkorn, breaking a longstanding taboo on criticizing the monarchy.
The police source, who declined to be named because he was not authorized to speak to the media, said the protest leaders had until November 30 to answer the summonses, which were brought over comments made at protests on September 19 and 20.
One of the seven, Parit “Penguin” Chiwarak, told Reuters his family had received a summons on the charges.
Others named included human rights lawyer Arnon Nampa, who became the first to call for royal reforms on August 3, and Panusaya “Rung” Sithijirawattanakul, a student leader who set out 10 demands for royal reforms.