Steven Donaldson was found at Kinnordy Nature Reserve near Kirriemuir, Angus, by two members of the public at 5am on 7 June.
A 19-year-old woman and two men, both aged 23, were arrested on Thursday in connection with the 27-year-old offshore worker’s death.
They are due to appear at Forfar Sheriff Court on Monday.
Mr Donaldson’s white BMW M1 sports saloon car was last seen at 10.53pm on 6 June in Kirriemuir – in a direction that would take him to the site.
A vehicle believed to be his was seen stationary within the car park at around 11pm that evening.
“I would again like to thank all those who have provided information and assistance in connection with this inquiry so far,” said Detective Superintendent James Smith, of Police Scotland’s Major Investigation.
“Our investigation is still ongoing and I would encourage anyone with information they think could assist us, to please contact police on 101, or Crimestoppers on 0800 555111 if you would prefer to remain anonymous,” he added.