The one-minute video, believed to be shot on a school campus, shows the freshy sitting on the floor and surrounded by older students. One of them covers the youth's his head with a plastic bag and the other two young men then started kicking him with all their might, repeatedly for about 20 seconds.
The victim did not retaliate nor try to defend himself, while other students just stood by and refused to intervene.
No details were available of the school and or the students, and the severity of the teenager's injuries was not known.
However, the video sparked outrage among internet users.
Youtube user tiratana buapa posted: "Is this the future of Thailand. This is very evil, worse than ...."
Rub-nong is supposed to be a tradition for welcoming freshmen to a university or school to acquaint students with their peers.
There have been many cases of violent and humiliating hazing in the past, resulting in severe injuries and even fatalities.