The gunman was allegedly Praween’s henchman Thananchai Manmak, who was later killed in a shootout in Kanchanaburi on Friday.
Praween, meanwhile, turned himself in to Nakhon Pathom police late on Thursday afternoon.
On Saturday, Deputy National Police chief Pol Lt-General Surachet Hakpal summoned all 25 police officers and guests for questioning.
Meanwhile, forensic examination showed that the firearm used by Thananchai to shoot Siwakorn was allegedly owned by one of the police officers present at the party.
Investigators say that all evidence has been gathered and they are seeking arrest warrants for several people attending the party. Among them were four police officers who were also attending.
