Vo Duc Duy, 33, is being held for investigation on charges of "intentional infliction of injury," police in My Tho City of the southern Tien Giang Province said Sunday.
The incident occurred over one week ago when Duy and Khuu Ho Song Toan, 51, a local man, went to a café in My Tho after a drinking session.
Feeling fatigued, Toan lay down in a hammock to rest, but Duy suggested continuing their outing. When Toan declined, an argument broke out.
In a fit of anger, Duy grabbed a knife and attacked Toan, striking him multiple times. While still lying in the hammock, Toan used his hands to fend off the blows.
Nearby residents intervened when the knife fell to the ground. However, Duy retrieved the weapon and continued his assault before discarding it and fleeing the scene.
The victim was transported to the hospital with a severed finger and multiple injuries, leading to a 12% permanent impairment rating.