The accident happened at the Bang Yai intersection in Surat Thani as the ambulance rushed 30-year-old Anucha Noosuntia, who had been injured in an earlier accident in Tambon Khun Talay, to the hospital.
Two nurses, Piangsom Soompradit, 39, and Piyawan Chansuk, 29, were flung out of the ambulance and found unconscious on the road. Anucha died instantly, according to police.
Ambulance driver Chanchai Kueankaew, 42, suffered slight injuries to his legs and arms.
Police said the ambulance was struck by the pickup truck before hitting another car. The truck driver fled before police arrived at the scene and they are now examining CCTV footage to track him down.