Myuran Sukumaran was tipped off about the arrest of the four Bali nine mules and could have fled the country, but chose to return to a hotel where fellow Bali nine members were waiting in an attempt to save the two men.

According to information never revealed previously, the third in command of the Bali nine, Tan Duc Thanh Nguyen, has recalled "the greatest and most special moment that I will always remember about Myu is something no one will know".

He says Sukumaran, executed last week by an Indonesian firing squad, acted selflessly to save fellow drug smugglers Si Yi Chen and Matthew Norman.

"I wanna share something with all of you. In memory of Myu," Nguyen wrote in a message that was shared on Facebook.

His fondest memory, said Nyguyen, was not something Sukumaran did in jail, or his art.

"[It was] the fact that he cared and worried about the rest. Calm and collected. This is what I will always remember about him," Nguyen wrote.

"Myu could of panicked and left the country."

The revelation comes as the Australian Federal Police, which has been widely criticised for tipping off Indonesian police with information leading to the arrests in Bali and knowingly exposing the Bali nine to the death penalty, will hold a press conference on Monday.

Commissioner Andrew Colvin, Deputy Commissioner Mike Phelan and Deputy Commissioner Leanne Close will discuss the AFP's work during the Bali nine investigation.

They will also discuss the AFP's guidelines in relation to death penalty matters in 2005 and the procedures the organisation operates under today.

Nguyen told Fairfax Media he and Sukumaran were at Bluefin, a Japanese fusion restaurant in Kuta, the day of their arrest on April 17, 2005.

Sukumaran was tipped off about the arrests of Martin Stephens, Renae Lawrence, Scott Rush and Michael Czugaj, the couriers for the Bali nine syndicate who were apprehended at Bali's Ngurah Rai International Airport with heroin strapped to their bodies.

"There is a reason why code system are used. To alert if something goes wrong and flee the country," Nguyen wrote.

"Myu didn't pack up and left the country. No. He went back to the hotel where the other two were waiting. Moved them somewhere else, and telling them the most important thing at the moment was getting them out of the country safely. Calming them down and be aware [sic] what's happening."

Of all the Bali nine, Sukumaran had the best chance of escaping after their operation had been compromised.

He had been under surveillance by the Indonesian authorities but they did not know his name. He was known only to Indonesian police as "the black one" or "the negro".

I Nyoman Gatra, an Indonesian police intelligence officer who led a surveillance operation after the tip-off from the AFP, told the Denpasar District Court in 2005 that Sukumaran had not been listed on an AFP alert letter sent on April 8 about a week before the Bali nine were arrested.

"At first I thought he was a bodyguard," he said at the time.

Sukumaran, Nguyen, Chen and Norman were arrested the night of May 17, 2005, at the Melasti Beach Bungalows in Bali.

Sukumaran wasn't actually in the room at the Melasti when it was raided by police, as has been previously reported. He was outside standing guard and was pushed into the room when the police stormed the hotel.

Police discovered rucksacks containing 334 grams of heroin and a bag of pepper, to put sniffer dogs off the scent.

Andrew Chan was arrested the same day on an Australian Airlines flight about to depart for Australia. He had no drugs in his possession but several mobile phones.

Sukumaran and Chan were executed at 12.25am on April 29.

Nguyen, who is serving life imprisonment in a jail in Malang, East Java, told Fairfax Media that after he wrote about what had happened he felt so much better.

"I can finally let go now."