The injured Cambodian migrant, who was beaten up and knifed, was identified as Thad Eef, 37, a worker at a factory in the Bang Pu industrial estate.
His right arm was almost severed and he was rushed to Samut Prakan Hospital.
His sister, Pha, 39, told police that Thad attended a wedding of fellow Cambodians in the evening at a restaurant and while he was dancing, he got into a quarrel with a group of Cambodian workers from another factory.
Pha said she and her brother were walking home along a soi about two kilolmetres from the restaurant when they encountered the same group of Cambodians who beat Thad up and attacked him with a knife.
Police will check footage from security cameras in the neighbourhood to identify and arrest the attackers.