By Aukkarapon Niyomyat and Amy Sawitta Lefevre
BANGKOK (Reuters) - A Thai military court jailed three people on Wednesday, including an aide to the crown prince, as part of a major probe into a group of people who allegedly falsely claimed links to the monarchy.
Thailand's lese-majeste laws are the world's harshest and make it a crime to defame, insult or threaten the royal family. Anyone convicted of insulting the royals faces up to 15 years in prison for each offense.
The investigation comes at a time when the government is cracking down on perceived royal defamation with prosecutions skyrocketing since a May 2014 coup.
It also comes at a time of heightened anxiety over the health of 87-year-old King Bhumibol Adulyadej, who is convalescing at a Bangkok hospital after being treated by doctors for 'water on the brain', which has added to the political uncertainty shrouding Thailand since the coup.
"There were references to the high institution ... so we brought these three in order to jail them," Srivara Rangsibrahmanakul, assistant national police chief, told reporters.
"There might be others involved in this case and if there are we will proceed with a case against them."
The term "high institution" is often used by Thais to refer to the monarchy.
A police document seen by Reuters named a policeman and two civilians, including Suriyan Sujaritpalawong, an aide to Crown Prince Vajiralongkorn, as suspects.
Suriyan pleaded guilty. The two others pleaded not guilty.
Since taking power in 2014, the junta has vowed to aggressively pursue and prosecute violators of the law, including those who live abroad.
Military courts, which since the coup hear many lese-majeste cases, have handed down record-breaking sentences.
The probe follows a high-profile corruption investigation in late 2014 involving the police, military and several family members of Srirasmi Suwadee, the former wife of Vajiralongkorn.
Srirasmi, formerly known as Princess Srirasmi, relinquished her royal title at the height of that investigation.
Critics say Wednesday's jailing was part of an unrelenting clampdown by the junta as it ramps up prosecutions under the royal defamation law.
"The junta and the army are on a warpath against critics of the monarchy," a senior Western diplomat based in Bangkok, who did not want to be named because of the sensitivity surrounding the matter, told Reuters.
"We see this in its arbitrary use of the law often to, one suspects, get rid of political enemies."
The case will be tried in a military court.
(Additional reporting by Panarat Thepgumpanat; Writing by Amy Sawitta Lefevre; Editing by Nick Macfie)