Thailand suing Facebook over video of crop top-wearing king

Facebook is facing a lawsuit after Thai authorities took offence to an unflattering video of their king sporting a crop top in Germany that was hosted on their site.

A video of King Maha Vajiralongkorn walking through a Munich shopping mall wearing a top that looked more like a bra than a t-shirt was posted on Facebook and shared widely.

The top showed off his heavily tattooed body - but the ink is believed to be temporary judging by previous images taken of the notoriously private new king, who took over power after his father, King Bhumibol Adulyadej, passed away last year.

The footage of King Vajiralongkorn, believed to have been filmed in July 2016, is considered insulting to the Thai monarchy - a crime punishable by as much as 15 years in jail in the royal-loving nation.

While it is uncertain what grounds Thai authorities would have to force Facebook to remove the content, they are threatening to press charges if the video is still on its site come 9pm on Tuesday (NZ time).

The video has been geo-blocked by Facebook, which means it cannot be viewed by those in Thailand, but Thai authorities say there are still 131 pages on the social network that still have the video up.

The secretary-general of Thailand's National Broadcasting and Telecommunications Commission says they are taking the availability of the video very seriously.

"If even a single illicit page remains, we will immediately discuss what legal steps to take against Facebook Thailand," he said.

As many as 105 people have been imprisoned for insulting Thailand's royals in the last three years, according to the Worldwide Movement for Human Rights.