Workers climb scaffolding to install a portrait of Thailand's late King Bhumibol Adulyadej near the Grand Palace in Bangkok on October 19, 2016. Photo: Reuters/Athit Perawongmetha

Thai police are investigating 12 new complaints of royal defamation found on social media lodged since the death of King Bhumibol Adulyadej last week, a sharp rise amid intensifying scrutiny of anything deemed offensive to the monarchy.

The death last Thursday of the revered king, 88, after seven decades on the throne has plunged the Southeast Asian country into mourning and heightened sensitivity about the monarchy.

King Bhumibol was seen as a stabilizing figure in a country often racked by political turmoil.

Prime Minister Prayuth Chan-ocha has moved quickly to quash any uncertainty around the royal succession, saying Crown Prince Maha Vajiralongkorn would ascend the throne after a period of mourning that he had requested.

Insulting the monarch, the regent or the heir, known by the French-language term “lèse-majesté”, is a crime in Thailand that carries a jail sentence of up to 15 years for each case.

Police spokesman Kitsana Pattanacharoen said there had been 12 lèse-majesté cases since last Thursday, with arrest warrants issued for eight suspects and four already in police custody.

“Their crime was posting messages or pictures which insulted the monarchy on social media,” he told Reuters.

There were 70 cases in the two-and-a-half years from a May 2014 coup up to last Thursday, said Weerawat Somnuek, a researcher at Thai legal monitoring group iLaw.

“Twelve cases in a week is a lot,” Weerawat said.

In some cases, violence has erupted against individuals deemed disrespectful, while similar anger has erupted online against people whose posts have been seen as inappropriate.

Thailand’s main mobile telecoms operators have, at the government’s request, asked customers to report websites and social media posts deemed inappropriate or insulting.

The government also asked internet service providers to monitor content and inform platforms such as Facebook, Twitter and YouTube to block offensive content. Failure to do so would be considered a crime, the government said.