Police were called to the scene, the Ruean Mai Chai Nam restaurant located on Soi Lim Sui Jiu, between Saphan Hin and Nimit Circle, at 6.30 pm.
A staffer at the restaurant, Pawin Chomchan, had been rushed to Phuket Provincial Hospital for treatment to a stab wound in his right leg.
Police were told the assailant, known as Mr Charoenrit, had entered the restaurant and used a knife to stab Mr Pawin.
So far no motive for the attack has been explained by police.
Phuket City Police are now trying to track down Mr Charoenrit.