The U.N. human rights office says Thailand should bring its laws criminalizing insults against the monarchy in line with international law.

Office spokesman Rupert Colville made the appeal Tuesday, days after a Thai military court handed down what's considered the longest-ever sentence for the offense of lese majeste: A 35-year prison sentence to man for social media posts deemed defamatory to the monarchy.

Colville said his office was "very concerned by the rise in the number of lese majeste prosecutions in Thailand since 2014 and the severity of the sentencing."

It cited statistics provided by Thai authorities showing a sharp drop in the number of people who have successfully defended themselves against such charges, falling from about one-quarter of people charged in 2013 to just 4 percent last year.