Thirteen Thai nationals have been given prison sentences after being convicted of attempting to scam the casino at Marina Bay Sands out of around $1.02 million in a case described by a judge as “unparalleled both in terms of sophistication and sum cheated”.

According to a report from The National newspaper, Saturday saw the nine men and four women aged 24 to 53 receive sentences of between 12 and 17 months after they were convicted in a Singapore district court last month.

The syndicate was found to have stolen a playing card carrier from the casino at Marina Bay Sands on May 6, 2013, before taking it back to their hotel room and photographing the sequence of cards. The members then reportedly returned the carrier to the same cabinet from which it had been pilfered knowing that it would be used the very next day in games of blackjack. Six members of the group subsequently used their knowledge of the cards to win substantial amounts of cash via three hours of play in the early hours of May 7.

Prosecutors alleged that the enterprise had rehearsed their scheme earlier in Manila and at the Swissotel The Stamford Singapore and had even conducted a reconnaissance trip weeks earlier to test a key with which to open the locked cabinet. They also charged that the fraudsters from Thailand had attempted to hide their advantage by losing some games of blackjack before stating that the offenders had been caught based on suspicious activities captured on the venue’s extensive network of security cameras.

“This was clearly the largest syndicated casino cheating operation that had struck Singapore up to that point,” said District Judge Soh Sze Bian.

The 109-day trial involved 53 witnesses with Soh declaring that the jail sentences were “entirely appropriate based on the facts and circumstances of the case”.

The alleged mastermind of the scam, 53-year-old Soum Sengmanivong, was also charged and on bail but is reported to have died in Laos in April. However, the court ordered that its arrest warrant remain in force until it can obtain more evidence to the actual whereabouts of the accused.