Arnon Nampa, who plays a key role in the anti-government protests, has urged guards of demonstrators to stick to a peaceful approach, saying this will help the movement achieve success.
On his Facebook account, Mr Arnon said that he received this advice from "an aunt next door" while discussing politics over dinner in Chiang Mai.
"She said if guards on the front line stick to a peaceful approach, we will win," Mr Arnon said.
"If our guards get involved in clashes or do anything that appears to be violent, this will deal a blow to the entire movement. On the contrary, if guards remain calm and use peaceful means, we will win," Mr Arnon said.
He made the remark after a clip of a man throwing what appeared to be a smoke bomb during an anti-government protest on Sunday was shown on social media.
Piyarat Chongthep, aka Toto, the head of the "We Volunteer" group of security guards that provided security for the protesting People's Movement, said on Facebook after the protest that coloured smoke bombs were used to counter the police use of water cannons against protesters.
Meanwhile the anti-government People's Movement on Tuesday issued a statement apologising for an incident in which a member head-butted and injured a 52-year-old Russian man during an argument in Pattaya on Sunday evening.
Narathiwat "Kane" Khamma was later arrested and faces criminal charges over the incident.
Prime Minister Prayut Chan-o-cha warned both sides of the political conflict to avoid clashes and said the assault on the foreigner in Pattaya has seriously damaged Thailand's reputation.
