BANGKOK • Thai police fired water cannon and teargas at protesters marching on Parliament yesterday, and at least 18 people were hurt in the most violent confrontation since a youth-led protest movement emerged in July.

Demonstrators had converged on Parliament in central Bangkok to put pressure on lawmakers discussing changes to the Constitution. Protesters also want the removal of Prime Minister Prayut Chan-o-cha, a former army ruler, and to curb the powers of King Maha Vajiralongkorn.

Police used water cannon to disperse protesters who cut through razor-wire barricades and removed concrete barriers outside Parliament. Officers then fired teargas.

Thousands of protesters gathered at different points and the number grew into the evening.

Ambulances ferried the injured to hospital. Bangkok's Erawan Medical Centre said 18 people were hurt, 12 of them suffering as a result of teargas. It said one of those hurt was a police officer.

"This is brutal," said a 31-year-old volunteer with the Free Youth protest group who gave his name as Oh.

Bangkok's deputy head of police Piya Tavichai told Reuters: "Police had to use teargas and water cannon because protesters were trying to break through the barriers."

Government spokesman Anucha Burapachaisri said police had been obliged to act to keep parliamentarians safe.

The Royal Palace has made no comment since the protests began, although the King recently described Thailand as a "land of compromise" when asked about the protests.

Lawmakers had begun discussions on a road map for amending the nation's Constitution yesterday, with a vote on the pathway to any changes expected by today.

Parliament restarted the stalled process that is aimed at meeting one of the key demands of the protesters, who are seeking a fresh election under a new Constitution.

Anti-government protests have swept Thailand since July, with activists breaking long-held taboos about publicly criticising the royal family and questioning laws that stifle discussion of the monarchy.

While the youth-led demonstrations have been largely peaceful, they threaten to derail an economic recovery in the tourism-and trade-reliant nation.

Thailand's current charter has been a point of contention since its inception after Mr Prayut took power in a 2014 coup. Protesters and critics viewed it as instrumental in helping the royalist establishment retain its grip on power with Mr Prayut returning as the leader after the 2019 elections.

The charter allows the military-appointed Senate, whose powers demonstrators want scrapped, to vote for the premier.

A panel appointed by Parliament to study the charter amendments submitted a report to the lawmakers yesterday.

If Parliament ends up supporting a pathway to create a committee to rewrite the charter, the process of establishing a panel alone could take three to six months, according to Dr Punchada Sirivunnabood, an associate professor of politics at Mahidol University near Bangkok.

However, such a panel without representatives from the protest movement may not help resolve any issues, she added.

"What we would likely see at the end of the process is the establishment still keeping the structure that helps them keep the power," Dr Punchada said. "There might be changes in election laws and Senate power, but those changes would still facilitate the establishment-backed party in the elections. There won't be any changes to laws related to the monarchy."

Government spokesman Mr Burapachaisri had said on Monday the protesters' demands should be addressed by the parliamentary process, and that the government is willing to listen to all suggestions that could help Thailand move past the current economic crisis.

Earlier yesterday, hundreds of members of a pro-royalist group called Thai Pakdee rallied outside Parliament. They are against changing the Constitution and any dilution of monarchy powers.

"Amending the Constitution is going to lead to the abolition of the monarchy," their leader Warong Dechgitvigrom told reporters.

However, the protesters have said they do not want to abolish the monarchy.

REUTERS, BLOOMBERG