The prime minister's twin daughters are suing more than 100 people for allegedly posting defamatory comments about them on social media.
Lawyer Apiwat Khanthong on Wednesday lodged a defamation lawsuit with police on behalf of Thanya and Nittha Chan-o-cha.
He said the twins had hired him to take legal action against more than 100 social media accounts, particularly on Twitter, for libel and for breaching the Computer Crime Act. It is unclear who tracked down the accounts.
Mr Apiwat said police would also consider whether some politicians had supported the crime by sharing the information.
His clients were insisting the offenders be brought to justice.
The lawyer added Gen Prayut had had nothing to do with the filing of the lawsuit.
He also listed and rejected claims in several posts.
For example, he dismissed a claim the twins had switched to their mother's surname in order to escape a case involving alleged money-laundering against Gen Prayut.
A claim that Prayut transferred money to their foreign bank account was also groundless, Mr Apiwat said.
Gen Prayut transferred money to his twin daughters in 2013, the lawyer said, and this was listed in an assets declaration which was submitted to the National Anti-Corruption Commission in 2014 when Prayut became prime minister.
The money came from the sale of a land plot which belonged to Prayut's father.
Refuting a further claim the twins had failed their master's degree exam, Mr Apiwat said they had never pursued master's degrees and had never failed an exam.
He also dismissed a report that the twins lived in a UK mansion bought for them by a wealthy tycoon. They have never stayed for long periods in foreign countries, Mr Apiwat said.
In fact the last time they visited the UK was in 2015, when they travelled on tourist visas and stayed at a hotel.
Mr Apiwat also said the twins had no social media accounts and never posted photos on such platforms because they wanted to maintain their privacy and prevent anyone from using their names for personal gain.
Speaking in Sukhothai on Wednesday, Prayut said his twin daughters had come of age and had the right to protect their reputation.
