Three men aged between 17 and 55 were arrested after a fight broke out in Redhill at around 11.30am last Saturday.
A video of the brawl, which was making the rounds on Facebook, shows two younger men shoving, hitting and kicking an older man, who falls to the ground at one point.
Some passers-by, including a GrabFood delivery rider, can be seen trying to break up the fight at Block 88 Redhill Close while the men exchange insults.
A 55-year-old man was taken conscious to Singapore General Hospital.
Police are investigating.