Pattaya police said Antonio Lardo, with a 3cm laceration on his forehead, had died no more than two hours, according to a Khao Sod report.
Nattawut Chalermpong, a motorcycle taxi rider in the area, said he had seen Lardo sleeping in front of a convenience store near Soi 1 on the beach road three days ago.
He also saw Lardo prowling the beach, looking depressed.
Three hours before Lardo died, Mr Nattawut, 26, said he had seen him drinking water on the beach.
Police surmised he might have been depressed about something or was deceived by someone, forcing him to sleep on the streets.
He might have tried to kill himself by jumping into the sea and might have hit a rock in the process.