The 44-year-old Dutchman “intentionally insulted King Willem-Alexander”, accusing him of being a murderer, thief and rapist, the Dutch judiciary said in a statement.
The man also doctored images of executions online to include the king’s face in place of those of the actual victims, it said.
He was found to have violated the king’s dignity, “specifically relating to the king’s constitutional position and its importance for the national interest”.
“This behaviour is unacceptable in our society and demands that a penalty be imposed on the suspect.”
Although the court in Overijssel, in the country’s northeast sentenced him to 30 days imprisonment, of which 16 were suspended, the man will not face any further time in prison having already spent 14 days in preventative custody last year.
The Netherland’s progressive D66 party has proposed scrapping the so-called “lese majeste” laws that make it an offence to defame the king, according to Dutch news site Nu.nl.
King Willem-Alexander, who according to Nu.nl supports an examination of the laws, has pledged to accept the outcome of any debate on the issue.
The issue of the laws banning defamatory speech against the royals last flared up in November 2014 when an activist shouted “Fuck the King, Fuck the Queen and Fuck the Royal House” during a protest.
Though the prosecutor initially filed a suit against the protestor, the decision was subsequently reversed after an outcry over the move that was condemned as an assault on freedom of speech.
The law banning defamation of the royal household has been on the statute books since 1881 and carries a penalty of up to five years in prison or a fine of 20,000 euros ($22,000) for those convicted.
In practice prosecutions are rare with just 18 brought between 2000 and 2012 — only half of which resulted in convictions, according to public television.