Kasetsart University's deputy rector on Monday lodged a legal complaint against a couple who filmed their outdoor sex session at the Bang Khen campus in Bangkok.
Damrong Sripraram acted after the clip went viral on social media on Saturday.
Investigating officers at Bang Khen police station have narrowed down the location of the sex act to the university's tennis court. But efforts to track down those responsible for making and posting the clip have proved fruitless after the Twitter account on which it appeared was closed down. Subscribers to the account were asked to pay 300 baht to enter groups sharing sex videos, then a monthly fee of 150 baht.
Pol Maj Gen Pattana Petsayanawin, chief of Metropolitan Police Division 2, said the suspects were being traced though security camera footage of cars entering the campus just before the sex act took place.
Police were seeking the owners of several vehicles that arrived at the university around 11pm and left at midnight, he added.
He said the lewd public act took place between Jan 6 and 8 at a time when only one campus gate, on Ngam Wong Wan Road, was open. University authorities have vowed to ramp up security operations over the entire 840-rai campus, which covers both university and demonstration school areas.
"Security measures must be tightened because our university grounds also host children over a wide age range, since their school caters to grades 1 to 12 and is part of our educational institution," Mr Damrong said.
"In addition, our university students are also concerned about safety. For their security, students of all ages need our protection. We have been entrusted with that responsibility, so I will never let anyone commit such a breach of it again."