Former prime minister Thaksin Shinawatra reported to public prosecutors on Tuesday morning and was taken to the Criminal Court for arraignment on his lese-majeste case.
The Office of the Attorney-General said the court accepted the case at 8.56am on Tuesday, officially making Thaksin a defendant.
Thaksin, 74, is accused of defaming the monarchy during an interview with a South Korean newspaper on May 21, 2015. In the interview, he claimed privy councillors supported the 2014 coup that ousted the government of his younger sister Yingluck Shinawatra.
Police alleged that the comments made during the interview violated Section 112 of the Criminal Code, also known as the lese-majeste law, as well as the Computer Crimes Act.
The computer crime charge is related to Thaksin inputting information into a computer system that was deemed a threat to national security.
Thaksin, who denies any wrongdoing, could face pre-trial detention if he is denied bail by the Criminal Court.
The lese-majeste law carries a maximum jail sentence of up to 15 years.