Crowds estimated to number in the tens of thousands led by local administrators gathered in several provinces around the country on Wednesday in a show of loyalty to the monarchy.
The royalist demonstrations, staged in response to recent calls by some student protesters for reforms of the monarchy, took place in provinces including Chiang Mai, Chon Buri, Lampang, Nan, Narathiwat and Songkhla.
Some of the rallies were organised as part of ceremonies to mark the 120th birthday anniversary of Princess Srinagarindra, the late grandmother of His Majesty the King and the late mother of His Majesty King Bhumibol Adulyadej The Great.
In Songkhla, thousands of people wearing yellow, the Thai traditional birthday colour of the King, gathered in Ranod and Sathing Phra districts. In Narathiwat, an estimated 20,000 yellow-clad people marched in Sungai Kolok district.
Similar gatherings have been planned in the provinces before the end of this month.
The royalist demonstrations come after recent mass rallies in Bangkok and other parts of Thailand called on Prime Minister Gen Prayut Chan-o-cha to quit.
At Ramkhamhaeng University in Bangkok, pro-monarchy groups on Wednesday announced they would protect the royal institution.
Pansuwan Na Kaew, a representative of Ramkhamhaeng University students and alumni, read a statement that condemned the Oct 14 anti-government demonstration when protesters flashed the three-finger salute at the royal motorcade of Her Majesty the Queen which was passing along Phitsanulok Road.
The statement said "those who pulled the strings behind the incident must come out to take responsibility".
The groups urged young people loyal to the monarchy to gather on Oct 31 at Ramkhamhaeng University.
Tossapol Manunrat, a representative from vocational student group Acheewa Chuay Chart, said the groups would not resort to violence and would not confront the opposing protesters.
The groups announced it would stay at Ramkhamhaeng University to monitor the anti-government demonstration on Wednesday evening.
Scuffles took place a little after 5pm on Wednesday between the group and anti-government People's Party protesters who came to the university.
The anti-government group moved to outside Huamak Police Station while the university asked the royalist group to leave the campus.
Prominent figures who previously rallied with the pro-monarchy People's Democratic Reform Committee (PDRC) have signalled their plans to take to the streets again.
Actress Nok Sinjai posted the question "Are you ready?" in her Instagram story on a yellow background with hashtags such as #protectthemonarchy #welovetheroyalinstitution and #welovetheking.
Taya Teepsuwan, wife of Education Minister Nataphol Teepsuwan, tweeted there are may more people who love the royal institution but they don't want to come out to demonstrate while the country is in the midst of a crisis.
A social media post of ex-PDRC leader Suthep Thaugsuban read: "I respect, admire and support those who come out to protect the monarchy in many provinces. I salute them for their great hearts that put nation, religion and the monarchy above all else."