A 44-year-old Thai actress was found dead after reportedly falling off a speedboat in a river in Bangkok.

Nida Patcharaweeraphong was with five other friends on board a speedboat heading to a restaurant when she fell in Chao Phraya river on February 24. She was reportedly seated on the back part of the boat but how she fell remains unclear.

The speedboat went looking for her for 20 minutes after her friends noticed she was missing but later decided to call local the rescuers who sent a team of 30 divers to scour the area.

Nida, whose nickname was Tang Mo, was found two days later on Saturday February 26, floating in the river around 300 metres away from Pibulsongkram Pier where she was last seen.

The actress' brother Dais Dejjab who joined the search and rescue mission was reportedly the one who spotted 'something floating' in the water and later positively identified it as Nida through her clothes.

He said: 'The pain everyone in the family is going through is unbearable. We loved our sister so much and she brought us so much happiness.

'I would like to thank everyone for their efforts. I came to take her back home now.'

Nida's devastated mother Panida Siriyuthyothin said the actress was a good swimmer so she could not believe what happened.

She said: 'Before that night she went missing I suddenly thought about her. I wanted to call her. When I heard the news, I could not believe it. I still hoped it wasn't her.'

Doctors who did an autopsy on Nida later that day confirmed her cause of death was drowning while a deep gash on her left leg was caused by the boat propeller.

Police Major General Paisarn Wongwatcharamongkol of Nonthaburi police said the owner of the speedboat may face charges for operating the vessel with an expired license.

He said: 'We found that the speed boat had an expired license and the person who was driving it at the time Nida fell also had no license to drive.

'The two may face charges for causing death due to negligence but no formal charges have been filed.'

The speed boat's owner Tanupat Lerttaweewit and the driver identified as 'Bert' have been taken to the police station for questioning.

Nida's body was returned to her family for funeral arrangements while investigations are ongoing.