A Chinese "slapping therapist" extradited from the UK has been charged with the manslaughter of a six-year-old diabetic boy in Sydney in 2015.

Hongchi Xiao, 53, has promoted the controversial practice of Paida Lajin which advocates slapping skin to release toxins from patients.

The six-year-old, a type-1 diabetic, died after he was found unconscious in a Hurstville hotel on Forest Road after his parents allegedly took him to a self-healing conference conducted by Xiao in late April 2015.

Ambulance paramedics attempted CPR but he couldn't be revived.

Xiao was arrested at a London airport on 25 April this year and later consented to return to Australia to face charges over the boy's death.

He arrived back in the country on Thursday morning and was arrested by detectives after landing in Sydney shortly after 5pm.

He was charged with manslaughter at Kogarah Police Station and is due to face Central Local Court later on Thursday. Police say he was refused bail.

The boy's 56-year-old father, 41-year-old mother and 64-year-old grandmother were arrested earlier this year and granted conditional bail after also being charged with manslaughter.

A UK court in June heard Xiao was also being investigated by British police over the death of a 71-year-old woman who had undergone slapping therapy.

The judge declined a bail application by Xiao, saying there was no way to ensure he wouldn't continue therapy workshops "which at the moment are said to have led to the deaths of two people".