Revered King Bhumibol Adulyadej, 86, is protected by one of the world's toughest royal defamation laws -- anyone convicted of insulting the king, queen, heir or regent faces up to 15 years in prison on each count.
"An unprecedented number of people have been charged with lese majeste offences... With fourteen charges or prosecutions initiated since the coup," Amnesty said in a report about rights since the military takeover on May 22.
Last month two activists were charged with breaching the law during a university play, which featured a fictitious monarchy, staged in October 2013 on the anniversary of a student-led uprising.
In another recent case, a 28-year-old musician was sentenced to 15 years in jail for writing insulting Facebook posts about the monarchy between 2010 and 2011.
Junta chief and recently appointed prime minister, Prayut Chan-O-Cha, has said he was forced to take power after months of protests against Yingluck Shinawatra's administration left 28 people dead and hundreds wounded, effectively paralysing her government.