Workers from the Fine Arts Department have removed graffiti that foreigners sprayed on the wall of the famous Tha Phae gate in Chiang Mai early on Thursday morning.
They cleaned the wall and removed the message left at the gate, one of the city's best known landmarks, the CM108.com Facebook account reported.
CM108.com ran the story and a video clip showing four foreigners walking along the road at the gate shortly before 4am. Two of them were seen writing a message on the wall.
The message seeems to be "Scougge Lee B", but a foreigner commented on the Facebook post that it actually was "Scouser Lee B", meaning Lee B from Liverpool.
The clip was taken from a nearby security camera at CoolMuang Coffee.
Viewers' comments rapidly escalated, accusing the graffitists of showing the city no respect and asking authorities to arrest them.
Thorranin Chaweechan, the coffeeshop manager, said he saw the graffiti when rewinding the recording to see what had been happening, and decided to post it on social media, the Chiang Mai News reported.
Pol Col Theerasak Sriprasert, chief of the Muang police, said the Chiang Mai Municipality had registered a complaint with police, and they were tracking down the four people.