“Bye Nior” is a common Tinglish (Thai English) term meaning “graduation party” (goodBYE to the seNIORs)., which this flyer posted on a window at Maha Sarakham University is apparently advertising.
As for the hos, I think they are trying to convey that they will be our hosts/hostesses.
So, does anyone want to go to a graduation party with a bunch of hos?