BAD GAL RIRI: Rihanna would certainly have to monitor her Instagram account if she was in Thailand, as she's a firm fan of the 'underboob selfie'.

Thailand's military government warned women on Monday against posting 'selfie' photos of the lower half of their breasts - a social media trend that has gone viral - saying their actions could violate the country's computer crime laws.

The 2007 Computer Crimes Act bans the creation of electronic content that might cause "damage to the country's security or causes public panic" in addition to "any obscene computer data which is accessible to the public".

In a statement on Monday, the government said this included the current underboob selfie trend, in which women take photographs of the underside of their breasts, often while lying on a beach.

The penalty for such actions is up to five years imprisonment.

"When people take these 'underboob selfies' no one can see their faces," government spokesman Anandha Chouchoti said. "So it's like, we don't know who these belong to, and it encourages others to do the same.

"We can only warn people to not take it up. They are inappropriate actions."

Underboob selfies have become a popular alternative to the traditional "lying on the beach" bikini shot, and have spawned many blogs and Facebook pages in Thailand.

Singer Rihanna shared an underboob selfie with her Instagram followers during a trip home to Barbados over Christmas last year.

It is unclear how law enforcement officials in Thailand would prosecute those taking the selfies, given that the photographer's face is not included in the image.

The underboob selfie ban is yet another method by which Thailand's military government are outruling Western influences in the country, since taking power in December 2014.

Film and music censorship, curfews and restrictions on public gatherings have also been implemented.