Police Colonel Krissana Pattanacharoen, deputy spokesman for the police force, said that the three suspects, all men, had been charged with taking part in a criminal syndicate, in addition to violations against the Computer Crime Act.
The suspects were identified as Udon Thani resident Danai Pairoh, Chon Buri resident Jatuporn Wattanaponlasak, and Nakhon Pathom resident Chaowalit Chomphai.
The military handed over a 19-year-old suspect to police on Monday for his alleged involvement in the apparently concerted hacking attacks. He was charged with the same offences as the other men.
Deputy Prime Minister and Defence Minister Prawit Wongsuwan had said that nine suspected hackers were arrested.
Five suspects remain in military detention and are expected to be handed over to the police soon for further legal proceedings, according to a source.