The pair, who were on their way out of the country, were identified as Joseph and Travis Dasilva, both 38 years old.
The two photographed their bared their buttocks outside the Wat Arun temple, and while they weren't nabbed on the temple grounds, the widespread sharing of the photo caught the attention of Thai police, who can take disrespect to the nation's royal and religious landmarks seriously.
"The two American citizens have admitted taking the picture," district police chief Jaruphat Thongkomol told Reuters.They were fined $153 dollars for public indecency and inappropriate behavior.
The tourists uploaded the photo on their Traveling Butts Instagram account, which contains similar photos at other famous landmarks around the world and has 547 followers.
"Once they are through with the charges, the Thai immigration police will revoke their visas and push for deportation," Col Choengron Rimpadee, deputy spokesman for the Thai immigration police, told BBC.
"They will also be blacklisted from coming back to Thailand," he added.
The police also claimed that they are preparing more charges against the tourists for posting their naked photos on the internet, which violates the country's computer law forbidding the posting of pornographic pictures online. The couple is also suspected of committing a similar act at the Wat Trai Mit Witthayaram temple in Bangkok, which contains the world's largest solid gold Buddha image.