Suraj Kumar Sarabajeet, 22, posed as an army captain and ordered 11 Apple MacBook Pro Laptops from Sapura Synergy on behalf of Singapore's Armour Headquarters in January last year.
He gave a fictional address in the email to Sapura and hired a courier company to collect the goods worth SGD 28,844.
But he sold these laptops for SGD 23,150 later that day.
Six days later, Suraj used the same ruse and ordered eight Apple MacBook Air laptops worth SGD 15,230 from Multimedia Integrated.
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In March 2012, he posed as a Federal Express executive and ordered 27 iPads, iPhones and laptops worth SGD 41,111 from retail Epicentre which he later sold for SGD 32,170.
Suraj duped his victims with SGD 135,772 worth of goods over a three-month period, all while he was undergoing two years probation for the similar offences.
The District Court on Friday convicted Suraj on 10 charges of cheating and forgery.
Suraj, who was pursuing a diploma in law and management, has been held in custody since April 11 last year.
"The accused ran multiple independent devised schemes, sometimes running the same con on the same victim more than once," said the prosecution.