A 24-year-old man has taken his own life after surviving a car crash that claimed the lives of his two best mates at Lake King on Saturday morning.

It is understood all three men, who hailed from nearby towns in Southland on New Zealand's southernmost tip, were not wearing seat belts.

Police said a passerby found the rolled ute on a straight stretch of the unsealed Lake King-Norseman Road in the Great Southern district, 470 kilometres south east of Perth, and called police at around 7.15am.

Three men's bodies were found in the wreckage of the car, but police said only two of them had died as result of the injuries received in the crash.