Kader, 22, was last seen getting into a client’s car before her body was found in the posh neighbourhood of Zekeriyakoy.
A missing person’s report was filed last week after the victim’s partner alerted authorities that she had not returned home.
Her burnt corpse was later positively identified at the city morgue. Kader had previously been pictured at LGBT rallies and was filmed being arrested by police at a demonstration in Istanbul.
This latest murder comes less than two weeks after the beheading of a gay Syrian refugee whose body was found a few miles from where Kader was discovered.
Muhammed Wisam Sankari, who had fled war torn Syria, was found decapitated after being raped and assaulted.