A long-term resident, Jufer, was arrested in the northern city of Chiang Mai after black paint was sprayed on several portraits of King Bhumibol, 79, whom many Thais regard as semi-divine.
Police are seeking five consecutive jail terms for Jufer, whose case has received almost no coverage in the Thai press.
"This is a delicate issue and we don't want the public to know much about it," Manoon Moongpanchon, the local chief prosecutor said.
Few other countries have lese majeste on the books and prosecutions are infrequent.
In 2001, four young people were fined for throwing a cream pie at King Carl Gustaf, Sweden's first treason case in living memory.
In Japan, where tabloids engage in detailed gossip about royals that would be unheard of in Thailand, lese majeste was repealed after the Second World War by General Douglas MacArthur.
MacArthur, who headed the post-war occupation authority, wrote that the Emperor "is entitled to no more and no less legal protection than that accorded to all other citizens of Japan".
For most Thais, only the most delicate portrayal of the world's longest-reigning monarch and his family is acceptable.
Foreigners are expected to show similar respect, and not doing so can have serious consequences.
A French businessman was arrested in 1994 for insulting the monarchy during a Thai Airways flight from London with two members of the royal family on board. He was later acquitted.
Other foreigners have run afoul of the law occasionally, but jail terms are rare. It can be more serious for Thais.
In the 1980s, Veera Musikapong was jailed briefly and banned from politics after he said in a campaign speech he would have a happier and easier life as a prince than a
Perhaps no one has tangled more with the law than Sulak Sivaraksa, a social critic charged in the 1980s and the early 1990s when he criticised the then-ruling military junta.
He was charged twice last year for what he says was criticism of Thaksin Shinawatra, the prime minister, later ousted in a bloodless September coup after a prolonged political crisis.
"This law has been used against people who are critical of the government," he said. "This law protects those in power."
Time for change
A major problem is that the law is vague and almost anyone can level an accusation of lese majeste, thereby triggering a police investigation, said Somchai Preechasinlapakul, dean of the faculty of law at Chiang Mai University.
"Often during political turmoil, the law is exploited as a tool to attack political opponents," he said.
Last year, Thaksin and his enemies hurled scores of lese majeste accusations at each other. Thaksin's alleged disrespect for the monarchy was one of the reasons for the coup.
"I am not afraid if the criticism concerns what I do wrong, because then I know. Because if you say the king cannot be criticised, it means that the king is not human "
King Bhumibol Adulyadej of Thailand
To prevent abuse, the law could be amended so that only certain state agencies could file charges, Somchai said.
Other analysts believe now may be the time to change a law they say stifles political debate in Thailand.
"With the prestige of the monarchy at its zenith and with an interim government that is unmistakably royalist, conditions are perfect for the reform or even repeal of the law of lese majeste," Grant Evans, an anthropologist wrote in a commentary.
King Bhumibol referred to the issue in his 2005 birthday address when he said he was not above criticism.
"Actually, I must also be criticised. I am not afraid if the criticism concerns what I do wrong, because then I know. Because if you say the king cannot be criticised, it means that the king is not human," he said.
But few Thais have taken the chance, or even dared to call for the repeal of the law.
"Those who do so will be deemed as showing their disloyalty to the revered monarch, which is a severe accusation," Somchai said.