The advice of a Chinese "slapping therapist" delivered at a week-long self-healing conference in Sydney influenced the 2015 death of a six-year-old diabetic boy, NSW Police allege.

Hongchi Xiao was arrested in London in April 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 charged with manslaughter at Kogarah Police Station.

He's due to face Central Local Court later on Thursday.

The six-year-old, a type-1 diabetic, was found unconscious in a Hurstville hotel after his parents took him to the self-healing conference conducted by Xiao.

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

"The seminar was a self-healing clinic run over the course of a week," Acting Inspector Brett Van Akker told reporters on Thursday.

"Police will allege that it was the advice that was provided during the course of that seminar by (Xiao) that has been an influence on the death of that child."

Xiao is reportedly cooperating with police but declined to an interview with investigators, the acting inspector said.

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.

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

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".

Police say the six-year-old's parents took him to the self-healing conference in Hurstville in late April 2015.

Late on April 28 emergency services were called to a nearby hotel following reports the boy had been found in an unconscious state.