Pawana's real name was Aranyaporn Laosaengthong. She was dubbed the "Pearl of Asia" during her acting career from 1960 to 1979.
She was believed to have fallen in the pool and drowned, but police had not ruled out the possibility of murder.
Pawana's partner, Nattapong Luangsirikul, 57, who has been living with the former movie star for about 10 years, said Pawana often visited the pool.
He believed Pawana fainted and fell into the pool, which is about 1.5 metres deep.
The couple run a pomelo vending stall in front of their house.Nakhon Chaisi police investigator Pinyo Musiksarn, however, said police had yet to conclude that Pawana's death was an accident.
Pol Lt Col Pinyo said Mr Nattapong gave confusing statements to police, while their neighbours told police the couple often fought.
Apicha Laosaengthong, 21, an adopted son of Pawana, said an employee of his mother's called on Sunday at 6pm to say Pawana was missing.
He rushed to her house, but Mr Nattapong refused to let him inside.
Mr Apicha said he learned that his mother's body was found about 3am yesterday. The Forensic Medicine Police General Institute will today conduct an autopsy to establish the exact cause of her death.
Pawana, nicknamed Yin, was born on Dec 20, 1943 to a Mandarin Chinese family. She began her acting career in 1960, taking a leading role in the film Saeng Soon, along with late actor Mitr Chaibancha and actress Amara Assavanonda.