Singapore's chief executioner, who claims he was fired after talking to the Australian media, still hopes to be called on to hang convicted Australian drug trafficker Van Nguyen.

Darshan Singh has threatened to sue his government for unfair dismissal if he he is not allowed to hang Australian Nguyen Tuong Van at 6am on Friday.

The 73-year old has hanged 850 prisoners in 46 years, and says he will do the job effectively. His published statements have him worried about the prolonged suffering of Ngyuen.

Singh has been caught in a media storm since media reports revealed his identity four weeks ago. He says, "I have been told I will not be doing this one. But, I have no idea who will be able to do this. No one has been trained to take over."

Singapore's prison department says Singh had not been fired and was still a contract officer. But, it did not say who would perform Nguyen's execution.