Bali Nine ringleaders Andrew Chan and Myuran Sukumaran have begged an Indonesian court for forgiveness and a second chance at life.

As part of their final appeal against their death sentences, the Sydney men told Denpasar District Court of their deep remorse for their roles in a 2005 attempt to smuggle more than eight kilograms of heroin from Bali to Australia.

Lawyers for Chan and Sukumaran have asked for the pair's sentences to be reduced to 20 years in prison.

The two men read statements saying they regret their actions and are sorry for their involvement in the heroin-smuggling ring.

Speaking in Indonesian as a mark of respect to the court, they told the panel of three judges that they had changed their ways and wanted the chance to be useful members of society.

Sukumaran, 29, said he was "truly, deeply sorry" for his actions and was now trying to lead a generous life, not a selfish one.

"I now realise that before I was arrested I was thoughtless and ignorant," he said.

"Before I was arrested I had no idea how harmful my drug crime would be.

"I did not think about the impact, I did not know any drug addicts and I never thought seriously about the consequences of my actions.

"From the bottom of my heart I can honestly say I am now a different person and a reformed person."

Chan and Sukumaran have both been running education courses for fellow inmates inside Bali's Kerobokan Prison as part of their efforts to rehabilitate.

Chan, 26, said he knew he could not change the "stupid things" he did in the past.

"But I have genuinely changed my behaviour and I really want to focus on what I can do now and in the future," he said.

Chan, who has also been studying for a bachelor's degree in theology while in prison, said he hoped to become a minister or a counsellor so he could help others avoid his mistakes.

"I accept that I deserve to be punished for my crime but I beg the court that I not be executed," he said.

"I hope I am given another chance in life."

Both men apologised for previously pleading not guilty, blaming bad advice from their previous legal team.

They also apologised for their behaviour at earlier court appearances, conceding they did not show appropriate respect.

Chan and Sukumaran were two of nine Australians convicted over the drug smuggling plot.

This final appeal, known as a judicial review, seeks to have their death sentences reduced to 20 years jail.

The appeal rests on evidence that the men have been successfully rehabilitated and are now role models inside prison.

It also argues previous rulings against them erred by finding them guilty of exporting drugs, even though they were caught before exportation actually occurred.

The appeal also argues that earlier decisions were also in error because they contravened international laws, adopted by Indonesia, that reject the use of the death penalty against narcotics criminals.

If the appeal fails they will be left with just one last unlikely chance for survival: clemency from staunch anti-drugs president Susilo Bambang Yudhoyono.

Fellow Bali Nine death-row inmate Scott Rush also has a judicial review before the courts.

Five other members of the drug smuggling plot - Martin Stephens, Matthew Norman, Michael Czugaj, Si Yi Chen and Tan Duc Thanh Nguyen - are serving life sentences.

Stephens' judicial review is currently being considered by Indonesia's Supreme Court.

The final member of the drug ring, courier Renae Lawrence, is serving a 20-year sentence.

Chan and Sukumaran's appeal will return to court on October 8.

- AAP/ABC