(CNN) Thailand's justice minister has praised the taking of "social measures" against people who insult the monarchy.
General Paiboon Kumchaiya's comments come as police said they are investigating 12 people under Thailand's strict lese majeste law, which stipulates harsh punishments for defaming or insulting the royal family.
Paiboon warned that Thais "couldn't accept" actions that insulted the monarchy, and accused people "outside of the country" of instigating criticism.
Lese majeste: Thailand's most controversial law, explained
Lese majeste
Bangkok police stand watch before King Bhumibol's funeral procession.
Since the death of King Bhumibol Adulyadej last week, Thailand has been plunged into deep mourning. Millions of people across the country are dressing in black and gathering to pray for the king.
Emotions are running high, and there have been a few reports of people being confronted or even attacked over allegations they insulted the late king.
In eastern Thailand's Chonburi province, a 20-year-old man was arrested and charged with lese majeste for posting messages about the king on Facebook.
A group of people confronted the man at his house and brought him to the police station, where he confessed, police colonel Preecha Somsathan told CNN.
A video posted online shows the man being forced to kneel by men wearing black. He is then kicked and punched by a small crowd of people.
Thailand's King Bhumibol Adulyadej: A life in pictures
Thailand's Bhumibol Adulyadej was crowned king on May 5, 1950. News of the 88-year-old's death was announced Thursday, October 13, via a statement from the Royal Palace read on state TV. He was the world's longest-reigning living monarch.
Bhumibol, left, is pictured in 1935 with his older brother, the former King Ananda Mahidol, in Lausanne, Switzerland, where the boys attended school. King Ananda was 20 when he died of a gunshot wound under mysterious circumstances. His 18-year-old brother, known then as Prince Phumiphon Aduldet, later assumed the throne to become King Bhumibol Adulyadej.
Bhumibol and his future wife, Princess Sirikit Kityakara, are pictured in Lausanne in 1949. The couple married a year later at Srapathum Palace in Bangkok, Thailand.
The King and Queen pose with their children, Crown Prince Vajiralongkorn and Princess Ubol Ratana, on the steps of Bangkok's Chitralada Palace in 1955. Two more daughters, Princesses Maha Chakri Sirindhorn and Chulabhorn Walailak, were born in 1955 and 1957.
The royal couple ride with U.S. President Dwight Eisenhower during a five-day state visit to the United States in 1960.
The King, far right, plays the saxophone during a 1960 jam session with legendary jazz clarinetist Benny Goodman and his band in New York.
The King walks with his wife and their 13-year-old son, Crown Prince Vajiralongkorn, during a visit to Britain in 1966.
The King convenes the first meeting of his country's National Reform Assembly during a ceremony held in Bangkok in 1976. The King put the monarchy at the center of Thai society, acting as a force for community and tradition even as the country flipped between political crises and military coups.
The King raises a camera to take a photo in 1995. He was given his first camera in 1934, which ignited a lifelong enthusiasm for photography. He has often been seen with a camera around his neck during public appearances.
The King and Queen survey a rice crop made possible by a Royal Irrigation Project in 1996. The project formed part of the Royal Development Projects, which focused on developing remote rural areas. The King has taken an interest in environmental projects throughout his long reign.
The King reviews an honor guard with Queen Sirikit and Crown Prince Vajiralongkorn during the annual military parade to celebrate his birthday in 2006.
The King lights candles at a ceremony to mark Coronation Day in Bangkok in 2007.
The King is wheeled towards his yacht in 2010, during a rare public appearance to open a new flood gate and two bridges in Bangkok.
The King is pictured with family members in 2012. He addressed a crowd from a balcony on his 85th birthday.
The King is seen through a car window as he leaves the Siriraj hospital in Bangkok in 2015.
A portrait of the King is held on the eve of his 88th birthday as people gather outside the Siriraj hospital in 2015. The King of Thailand is regarded as a demi-god by many Thais, and his popularity has been viewed as a unifying force during times of political unrest.
In a separate incident, a 43-year-old female tour guide was arrested the popular tourist resort of Koh Samui.
She is currently being held in Koh Samui prison on suspicion of lese majeste, but denies the charges, police captain Boonnak Srinarat told CNN.
Video of her arrest shows police making her kneel in front of a portrait of Bhumibol as bystanders take photos.
Thai police could not release details of what the two people are accused of saying, as to do so would in itself breach lese majeste.
Thai King Bhumibol Adulyadej dies at 88
A Thai cyclist prays in front of the Grand Palace in Bangkok on October 16, 2016. Thousands of Thai men and women gather daily in the vicinity of the palace to pray for the late Thai King Bhumibol Adulyadej after his death Thursday.
A Buddhist monk stands next to line of mourners waiting to pay their respects to the body of the late King Bhumibol Adulyadej at the Grand Palace in Bangkok, October 15, 2016.
Devotees light candles for the late Thai King at Mahabodhi temple in Bodhgaya on October 14.
A Thai man carries high an image of Thailand's King Bhumibol Adulyadej as a large crowd floods the streets leading to the Royal Palace on October 14, 2016.
A van carries the body of Thai King Bhumibol Adulyadej's to his palace in Bangkok on October 14.
Thais gathering outside of Siriraj Hospital in Bangkok hold up baht notes with a portrait of Thailand's King Bhumibol Adulyadej on Friday, October 14, in Bangkok, Thailand, following news of his death the previous day.
A flag flies at half-staff outside a government hospital on October 14 in Chiang Mai, Thailand. According to a palace statement, all government buildings will fly the Thai flag at half-staff for 30 days starting on Friday.
Thai Prime Minister General Prayuth Chan-o-cha attends a traditional funeral bathing ceremony for the King at the Grand Palace in Bangkok on Friday.
The Prime Minister arrives to pay respects to the late King at the Grand Palace on October 14.
Dignitaries participate in a ceremony commemorating the King at Wat Phra Singh on Friday in Chiang Mai.
Buddhist monks line up to offer condolences at the Grand Palace in Bangkok on Friday.
People dressed mostly in black wait outside the Grand Palace to pay respects to the King on October 14.
The Thai Royal Guard marches in honor of Thai King Bhumibol Adulyadej on Friday.
Amid a procession of vehicles, a van carries the body of the King to his palace in Bangkok on Friday.
Mourners shade themselves under umbrellas while they await the procession of the King's body to the palace in Bangkok on October 14.
A woman passes out after an official statement announces the death of the king.
People react to news of the King's death outside Siriraj Hospital in Bangkok on Thursday.
A women cries after learning of the King's death on October 13 in Bangkok.
Sad scenes
Thailand remains in deep mourning for Bhumibol, with millions across the country dressing in black and gathering to pray for the king.
As the country comes to terms with losing the only monarch most Thais knew, questions about the timing of the succession remain unanswered.
Crown prince Vajiralongkorn is expected to become king in the next month or so, but has said he needs time to mourn his father before an official date is announced.