Saturday's incident was the second time in three months Ashvin Patel, the owner of the Sai Food Market on Prince Albert Rd, had been robbed.
In the latest incident, a man entered the shop at 9.36am, said nothing, and brandished a large knife at Mr Patel, who jumped from his chair behind the counter and fell as he scrambled to safety in a room behind the shopfront, from where he called police.
The man, meanwhile, allegedly slipped behind the counter, took several packets of tobacco, and ran from the store.
Mr Patel gave chase as the man ran south, turned left on to Victoria Rd, and then left into in Queens Dr before Mr Patel lost sight of him.
Police used a police dog in an extensive search of the area but they found nothing.
Mr Patel said the incident had left him bruised and shaken.
Almost exactly the same thing had happened in August, he said.
He believed the same person might have been involved in both incidents.
The robbery was recorded on CCTV, which the shopkeeper installed after the earlier incident.
The man, a slim Caucasian aged about 20, wore blue jeans, a black or dark grey top or hoodie.
A bandanna, or similar, covered his face.
Detective Sergeant Brett Roberts said he hoped someone had seen the man running off or taking off an item of clothing as he ran.
The man dropped several packets of tobacco during his escape.
