Thailand has begun a search for people deemed to have defamed its monarchy in the wake of the king’s death, investigating 20 new criminal cases and seeking to extradite suspects from abroad.

The country’s lèse-majesté (wounded majesty) laws are among the world’s strictest, meaning anyone who “defames, insults or threatens the king, queen, heir-apparent or regent” can face up to 15 years on each charge.

King Bhumibol Adulyadej, who spent seven decades on the throne, was seen as a unifying figure in a politically turbulent country. But his death, at the age of 88, on 13 October has led to both uncertainty and a heightened sensitivity over any discussion of the monarchy’s role.

Crowds have gathered outside the palace since the king died and, in an attempt to relieve tension, the authorities announced on Saturday that 10,000 mourners would be allowed to enter the throne hall of Bangkok’s Grand Palace – where the king’s body is lying – every day.

The ruling junta, which took power in a military coup in 2014, positions itself as being closely aligned with the monarchy and has sought to appease ultra-royalist factions by pursuing anyone deemed to have breached lèse-majesté laws.

National police chief Jakthip Chaijinda told reporters last week that arrest warrants had already been issued for eight of 20 suspects in Thailand. “For lèse-majesté cases, if people don’t want to live in Thailand they should go abroad,” Jakthip told journalists. “If they don’t have money for the air fare, I will pay for it. They can ask me to buy their plane ticket.”

However, the foreign ministry has also attempted to track down suspects abroad. It said last week that it had asked several foreign countries to extradite people accused of lèse-majesté. While it did not name the countries, a Cambodian official said that authorities were working on an appeal to extradite three Thais accused of insulting the monarchy.

The Cambodian foreign ministry spokesman, Chum Sounary, told reporters that its government “is processing the extradition request”. No specific details of their alleged offences were provided.

If they don’t have money for the air fare, I will pay for it. They can ask me to buy their plane ticket Jakthip Chaijinda, police chief

There is no legal definition for what actions constitute royal defamation, allowing judges to hand out what critics say are unreasonably harsh sentences. Political opponents of the military say they have used the law, Article 112, to silence opponents. In 2014 complaints were filed against a woman who wore black on the king’s birthday, and last year military courts jailed two people under the law, one for 30 years and the other for 28, for posts on Facebook.

Sensitivity about the monarchy is at a high point and the government has been under pressure to show that it is upholding the royal family’s reputation. Shortly after Bhumibol’s death, the prime minister declared a year of mourning, under which civil servants are expected to wear black. Thais and foreigners in the country have been told to wear black, white or grey for a month.

A high-level delegation – including the deputy prime minister – was sent to meet Google executives to push the company to remove any content that defames the royal family, including videos posted on its subsidiary, YouTube.

Public displays of grief have also been significant. Many websites, from the Bangkok Post newspaper to Tesco’s Thai site, have turned their homepages black. Thai Airways has waived fees for rescheduling flights for a month, and foreign leaders have flown to Bangkok to pay their respects. Hollywood actor Steven Seagal met the prime minister, General Prayuth Chan-ocha, to express his condolences. The domestic football season was cancelled to show respect for the late king.

But there have also been incidents since 13 October that highlight how deeply taboo any objective discussion of the monarchy has become.

Last week the justice minister said Thai people should “socially sanction” those who defame the monarchy. Days before, a Thai woman accused of insulting the late king on social media was forced to kneel before his portrait outside a police station in front of jeering crowds.

Bhumibol was formally known as King Rama IX, and was the ninth of the 234-year-old Chakri dynasty. His son and crown prince, Maha Vajiralongkorn, 64, is in line to become the next king but has asked that his ascension to the throne be delayed while he grieves with the Thai people.

General Prayuth later told the country that the heir apparent could become king between seven and 15 days after the king’s death, or later. An official coronation will not happen until after the funeral for the king, in a year’s time.