University officials were said to be investigating a March 23 video clip posted on YouTube on Sunday that purportedly showed a professor asking students to trade their 7-Eleven stamps in exchange for better grades, according to Thai Rath newspaper.
"I will give you a better grade if you bring me the stamps. But it is not mandatory, just a suggestion," the professor said in the clip.
One girl reportedly exchanged 400 stamps for an A grade.
The clip was posted online by a disgruntled student after university officials failed to act on her complaints, the report said.
7-Eleven stamps are part of a promotional campaign run by the convenience store. Patrons are rewarded with stamps for their purchases, which can then be traded for gifts and discounts.
Thailand is the third-largest market for 7-Eleven in the world, after Japan and the United States, with almost 7,000 stores nationwide.