Student activists who have been rallying across the capital must refrain from mentioning the monarchy or else they will face a public backlash, warned Jatuporn Prompan, chairman of the United Front for Democracy against Dictatorship (UDD).
Speaking to the House committee on national reconciliation on Thursday, Mr Jatuporn said the students must not drag the monarchy into their activism. If they did, the movement would be weakened because many citizens would not accept it, he added.
"It would end with huge losses like in the past," Mr Jatuporn said. He is understood to be referring to the student protests in the 1970s.
Unless the students steer clear of the topic of the monarchy and stick to their three demands -- charter changes, dissolution of the House and a stop to violations of people's freedom -- they would be defeated, he said.
The students will likely lose support from many if they offend the high institution, Mr Jatuporn added.
He insisted he does not intend to breathe fear among the student activists, but added he was concerned about the consequences of their actions if they are deemed offensive to the monarchy.
"I'd like to ask these students to keep a clear head and bear in mind that Thailand will [always] be governed by a constitutional monarchy that will serve as [the kingdom's] guard," Mr Jatuporn said.
He said their three demands could be discussed through parliamentary channels, noting however their call for the dissolution of the House and the amendments to the charter were contradictory.
According to Mr Jatuporn, disbanding the House would require either constitutional amendments or would come about through a general election, which would be governed by current rules.
Meanwhile, Piyabutr Saengkanokkul, co-founder of the Progressive Movement, took to Facebook on Thursday to ask if the authorities were genuinely ready to listen to the voices of young people. Problems have been accumulated through the generations, which everyone had a part in creating, Mr Piyabutr said, adding those problems are now being passed on to young people.
"If we are willing to open our minds to the voices of young people, we should also get down to finding a solution for this country together," he said. The House of Representatives on Thursdayvoted 260-178 to set up a committee to listen to the students.