BANGKOK — In unison, antigovernment protesters on Wednesday called the King of Thailand a giant monitor lizard, one of the worst things that can be said of anyone in Thai, and spray-painted bus stops and pavement in the capital’s central business district with graffiti describing his sexual activity.
The insults demonstrated the increased daring of protesters in a country where criticism of King Maha Vajiralongkorn Bodindradebayavarangkun, 68, can be a criminal offense, and the security apparatus has a history of crushing dissent. They have been gathering by the thousands across Thailand for months now, calling for the military-linked prime minister to resign and for the constitutional monarchy to actually come under the Constitution.
As demonstrators pushed their way to the gates of Thailand’s Parliament on Tuesday, one of their leaders, Arnon Nampa, stood on a truck that doubled as a stage and threw down a bold ultimatum to the nation’s governing elite.
“One day, if there’s no reform, we will revolt,” Mr. Arnon, a human rights lawyer, declared amid the whiff of tear gas.
The establishment has counseled patience. Last month, Prime Minister Prayuth Chan-ocha of Thailand, a former general who came to power during a military coup six years ago, withdrew an emergency decree aimed at the protests. He acknowledged that spraying water cannons at youthful protesters wasn’t the most productive strategy and said Parliament needed time do its job in tackling reform.
But on Wednesday, Parliament delivered its verdict: Certain parts of the Constitution may possibly be amended in the months to come, but not any sections related to the monarchy.
Hours before, on Tuesday night, police had again used water cannons to spray protesters with liquid laced with corrosive agents. Dozens of people were hospitalized, some with bullet wounds. And Mr. Prayuth remains prime minister.
Mr. Arnon, who has been charged with multiple counts of sedition and other crimes that could land him in prison for decades, expressed little surprise at the state of play.
For all the dynamism of the protesters — they have deployed humor, logistical prowess and oversized rubber ducky floats to protect against the water cannons — the demonstrations have, so far, catalyzed little change in how Thailand is ruled.
“If the house is too ruined, we shouldn’t fix it,” Mr. Arnon said in an interview on Wednesday. “We absolutely have no hope of reforming the monarchy through the Parliament.”
And so, he added, the rallies will now focus directly on the most combustible of the protesters’ demands: curbing the powers of one of the world’s richest and most powerful monarchies.
“Now, we fight face to face,” Mr. Arnon said. “There’s no hidden agenda.”
The protest on Wednesday was called with the slogan “If we burn, you burn with us.” Some demonstrators, who were incensed by the use of tear gas and water cannons the day before, threw buckets of paint at the police headquarters and covered nearby signs with denunciations of Mr. Prayuth and the king.
Just down the road, a spray-painted sign announced in English: “The King is Dead. Long Live the People.” A man urinated into a bottle and flung it at police officers standing in formation behind riot shields.
Shielded by some of the world’s strictest anti-defamation laws, the Thai monarchy has in a matter of months gone from an untouchable institution, whispered about only in private, to the subject of open criticism.
Protesters have asked why King Maha Vajiralongkorn has spent most of his reign outside of Thailand. Their taxes, they note, fund his stay in Europe. His complex family arrangements are the source of ridicule. (Last year, he married his fourth wife, named another woman the royal consort, then purged the consort for trying to upstage the queen. He restored her status in September.)
Most of all, the protesters have called for an investigation into the crown’s billions of dollars in wealth, which are now under the king’s personal control. He also has brought key military units under his command, with forces considered loyal to him quickly promoted.
Led by students and other youths, the Thai protest movement has embraced an array of issues, supporting gay rights and labor unions, and calling for an end to stringent school rules and a tax on menstrual products.
But the protesters’ increasingly direct condemnation of the monarchy — even as it is couched as a push for reform rather than as a move to topple the entire institution — has shocked some Thais. On Tuesday, demonstrators carried a large balloon with the phrase: “We told you to be under the Constitution.” That directive to the monarch used the lowest form of “you,” in a language that reflects multiple gradations of social hierarchy.
“The language used was something that’s unacceptable for Thais,” said Warong Dechgitvigrom, a prominent royalist. “Those aren’t the actions for reform, rather they are the actions to overthrow the monarchy.”
As tempers flared on Tuesday and Wednesday, it was hard to see the space for political compromise. The protesters have called for another mass rally in a week’s time.
“I would be lying to myself if I said there’s hope, and I would also be lying to myself if I said there’s no hope,” said Rangsiman Rome, an opposition legislator who tried unsuccessfully to push through some of the more controversial constitutional draft amendments on Wednesday.
In the background are fears that the security forces may crack down hard on protesters, as they have done with fatal force on multiple occasions. There are worries, too, that the military may unleash a coup, as has happened a dozen times since absolute monarchy was overthrown in 1932.
The palace itself has been largely silent on the protests. King Maha Vajiralongkorn returned from Germany last month and has been in Thailand for weeks, a rarity.
On Tuesday, around the same time that the water cannons began firing on protesters in Bangkok, he attended the graduation ceremony for a police cadet school in which he urged the graduates “to gain faith and trust from other people.”
Three days earlier, he attended the opening ceremony for a new Bangkok electric rail line named in honor of his official coronation last year. After greeting well-wishers, signing autographs and accepting cash donations from them — a break from the usual remove with which he has treated the public — the king settled into the seats of the train carriage with his queen.
At their feet knelt a row of men in white uniforms, a symbol of submission in Thailand’s modern-day constitutional monarchy.