The 69-year-old actress, whose real name was Aranyaporn Laosaengthong, was found dead in a pool at her house in Nakhon Chaisi district of Nakhon Pathom on Monday.
Pol Col Pornchai Sutheerakun, deputy chief of the Forensic Medicine Police General Institute, said an autopsy found a few minor bruises and wounds on her face, body and legs, but he said they may have been caused by her bumping into things.
The autopsy also revealed water in the lungs, showing she was alive when she came into contact with the water, Pol Col Pornchai said.
Police believe the actress fell into the pool and drowned, but her relatives think there are suspicious circumstances surrounding her death and are pointing to Pawana's wealth and troubled relationship history.
However, Pol Col Pornchai said police have not found any indication that Pawana was murdered.
Forensic experts had collected some DNA samples for testing, he said.
The results will be known in two weeks.
Pol Col Pornchai said Pawana might have passed out and fallen into the pool as she had suffered several illnesses recently.
Waipoj Laosaengthong, Pawana's younger brother, yesterday said he had some evidence to hand over to police investigators.
He believes she was assaulted. He said that shortly before her death he saw a bruise on her right eye.
Nakhon Pathom police chief Phetcharat Saengchai yesterday led a team of police to inspect the actress' home, located on a 16-rai plot.
Police would gather more evidence from the house, he said.
A source said the former actress had at least 20 cars and many land plots in Bangkok and other provinces. Her assets are estimated at several billions of baht.
Police questioned Pawana's partner, 57-year-old Natthapong Luangsirikul.
Mr Luangsirikul reported finding the actress's body.
Mr Natthapong yesterday said he had lived with Pawana for over 10 years and there were no reasons for him to assault his wife.
He runs a pomelo stall outside their house and said he always kept a low profile. He said the bruises found on her body might have occurred when he pulled her from the pool.
Funeral rites for Pawana are being held at Wat Makutkasattiyaram in Bangkok.