Defence lawyer M. Ravi said he had requested the hearing scheduled for Tuesday be delayed. The Court of Appeal has not informed him of a new date, the lawyer added.
The court didn't immediately reply to a request for comment from The Associated Press.
The hearing was originally scheduled for Nov 10, a day before Nagaenthran K. Dharmalingam was to be executed by hanging for trying to smuggle less than 43g (1.5 ounces) of heroin into the country.
The appeal was postponed after the defendant was diagnosed with Covid-19.
Previous attempts to reduce the 33-year-old Malaysian national's sentence to life in prison or receive a presidential pardon have failed, despite pleas from the international community and rights groups.
Death penalty opponents say Nagaenthran’s IQ of 69 was disclosed during an earlier lower court hearing.
That level is internationally recognised as an intellectual disability. But the court has ruled that Nagaenthran knew what he was doing.
The case has drawn widespread international attention.
Legal experts - including with the Anti-Death Penalty Asia Network and Amnesty International - have called the execution of an intellectually disabled man inhumane and a violation of both international law and Singapore’s Constitution. - AP