Webmasters face criminal charges for comments posted on their websites deemed offensive to the royal family.
Thailand's lèse-majesté laws are already strict, but a new crackdown on insults has resulted in a spike in arrests, including that of an Australian novelist.
The government denied attacking demonstrators, who have called for the ouster of the prime minister.
The ousted Thai prime minister, who returned Thursday, faces corruption charges and a divided nation.
The majority coalition is expected to name a controversial prime minister.