Double-murder suspect Panya Yingdung was flown to Bangkok on Tuesday night after being handed over to Thai police by Cambodian authorities at the border.
The 39-year-old Phuket club owner, also known as "Sia Ouan", is the key suspect in the murder of a young couple by two gunmen at Buddha Mountain in Chon Buri in late July. He fled to Camboia after the shooting.
He was escorted to a car immediately after the helicopter arrived at the Thai Police Aviation Division on Ram Intra Road in Bangok's Bang Khen district about 9.33pm.
He was to be questioned by the national police chief on Wednesday morning.
Mr Panya is alleged to be one of the two gunmen who shot Paweena Namuangrak, 20, and her male friend Anantachai Jaritram, 21, in the parking lot at Khao Chee Chan, also known as Buddha Mountain, in Chon Buri's Sattahip district on July 29.
Investigators suspect jealousy and vengeance were the motive for the killing as Paweena had worked in his club and was said to be his "favourite girl".
Mr Panya disappeared after the shooting, his pickup found abandoned near the Cambodian border in Sa Kaeo. He was arrested in Prey Veng province in Cambodia on Aug 15, reportedly heading to Vietnam.
He was charged with illegal entry into Cambodia.
Five other suspects in the double murder are already in police custody.