Thailand’s prime minister has ordered a second autopsy be conducted after the death of a key witness in a deadly hit-and-run case linked to the heir to the Red Bull energy drink fortune, amid public anger that the charges were dropped.Jaruchart Mardthong, 40, died in what police said looked like a motorcycle accident on Thursday, amid public suspicion about the exact cause of his death.Results of an initial autopsy have not yet been released. Local media said his family had planned to cremate…