Photos of the naked couple were shared in a local Facebook group in Chiang Mai on Sunday, showing two Thai police officers intervening in their sexual act.
On July 4, police were alerted by local residents, saying a foreign couple were engaging in sexual acts in public, Khaosod English news site reported.
As police arrived at the scene, they asked the couple to put on their clothes and took them to a nearby hospital for blood tests, where they found alcohol in their bodies.
The couple admitted to the police that they had smoked cannabis and consumed a large amount of beer and were unable to control themselves.
They have since left the hospital but have not yet returned to their home country.
Police are searching for the couple to conduct further legal proceedings, Thaiger reported.
Under Thailand’s law, those committing obscene acts or exposing themselves in public can be fined up to 5,000 baht (US$137).
In April, a foreign couple was charged with engaging in sexual activity at Patong Beach in Phuket.