In a posting on the popular portal Pantip.com, a Thai traveller who recently visited the Great Wall included pictures of Thai inscriptions bearing the names of other visitors to one of the Wonders of the World.
The traveller said that regrettably, inscriptions bearing the names and dates of people's visits could be seen in many languages but those in Thai seemed to outnumber others.
Viewers of the post criticised the writings as inappropriate, saying such actions showed no respect for the site and ruined its beauty.
Sisdivachr Cheewarattanaporn, president of the Association of Thai Travel Agents, said on Saturday that such behaviour could affect the image of Thai travellers in the eyes of Chinese people.
He urged authorities to verify the report but said the association did not intend to take any action relating to the issue at this time.