BANGKOK: Two American tourists have been held for "inappropriate behaviour" after sharing photos of them baring their buttocks at a famous Bangkok temple, Thai police said Wednesday, as the ruling junta cracks down on insults to Buddhism.

The pair, Joseph and Travis Dasilva, both 38, uploaded pictures on November 24 of their bared backsides at Wat Arun (The Temple of Dawn) to Instagram.

It was not immediatley clear if the men were related.

But their asinine antics could land them in more serious trouble after police sought to charge them under a draconian computer crime law -- an offence that can carry jail time.

The riverside temple, whose ancient 'prang' - tower - is the one of Bangkok's best known landmarks, features on the logo of the Tourism Authority of Thailand.

The men were detained at a Bangkok airport late Tueday and fined $150 each.

"They were detained as they were about to leave Thailand," Colonel Cherngron Rimpadee, an Immigration Police spokesman said, adding they were on a 'watch list' after their social media posts caught authorities' attention.

Colonel Jarupat Thongkomol, from the police station near the temple which is managing the case, said the men now faced more serious charges.

"We are now seeking court approval to prosecute them on Computer Crime Act for uploading pornographic pictures," he said.

The act carries up to five years jail per charge and is routinely slapped on political dissidents or people deemed to have insulted Thailand's monarchy.

Junta-run Thailand takes a hardline on disrespectful gestures towards Buddhism, the dominant religion in Thailand.

Tourists are told not buy and sell Buddha sculptures or get sacred tattoos or of images of the Buddha for fashion purposes.

People visiting temples are also expected to dress modestly, covering their shoulders and legs -- with advice signs common at Bangkok's religious landmarks.

In 2015 neighbouring Malaysia deported four western tourists after charging them with obscenity for taking nude photos on a mountain on Borneo island.-AFP