Pol Lt-Col Pinyo Muksiksarn, the duty officer at Nakhon Chaisri station, said on Monday that he received a report about 3am that Pawana's body had been found on the ledge of a pond near her house on Nakhon Chaisri-Pinklao road, near the Thai Human Imagery Museum.
Apicha Laosaengtong, Pawana's adopted son, told investigators that Pawana had been living with Nattapong Luangsirikul, aged 57, for more than 10 years. They opened a grapefruit shop in front of their house and hired two workers.
Mr Apicha, 21, said one of the workers phoned him and told him that Pawana had mysteriously disappeared. He then called Pawana's relatives to go to her house.
When he and Pawana's relatives arrived, Mr Nattapong angrily told them not to enter the house and to leave immediately because he was the house owner. Mr Nattapong also threatened him by firing a gunshot into the air, according to Mr Apicha's statement.
Mr Apicha said he was later informed of Pawana's death at about 3am.
Mr Nattapong told police that Pawana regularly paid respect to holy spirits near the pond and that she might have passed out and fallen into the water.
Another witness whose name was not given told police that Pawana and Mr Apicha had traded heated words prior to the incident.
Mr Nattapong was believed to be present at the pond where the former actress died and there were some conflicting issues to be resolved, police said.
An autopsy will be conducted on Tuesday to establish the exact cause of her death, police said.
Pawana, whose real name was Aranyaporn Laosaengthong, 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. She won an award for the film.
Dubbed the "Pearl of Asia", Pawana's acting career ran from 1960 to 1979.