Police said they and Victim Support were providing as much help as possible to his family, and were treating the circumstances surrounding his injuries as suspicious.
At around 8.30pm on April 28, Kimleang fell from a vehicle he was travelling in on Robertson Rd, Māngere, and sustained critical injuries.
This vehicle did not remain at the scene at the time and fled the area, police said.
Police have appealed for information or sightings of this light-coloured van or people mover, possibly grey in colour, which was believed to be involved. Photo / Supplied
"Our inquiry team has spoken with a number of people who came to Kimleang's aid after the incident, but there are still other people we would like to hear from.
"Police are aware that some people at the scene many have been recording at the time emergency services arrived. We ask that these people come forward and contact police."
Anyone who had witnessed events leading up to the incident or who had CCTV footage from around that time was also asked to contact the Operation Kinley team on (09) 261 1321, or Crimestoppers anonymously on 0800 555 111.