TJ McConnell holds the official record for the smallest hands in NBA history which is quite surprising considering his height of 6'1". His hand span or width has officially been measured at only a mere 7 inches. Isaiah Thomas stands 4 inches shorter than McConnell yet his hand span or width measures 9 inches. McConnell's hand length isn't impressive either at 7.5 inches. The average male who stands at just 5'9" has roughly the same hand length as him. Even 5'9" Isaiah Thomas has a hand length that measures 8.3 inches.
Height is usually a safe predictor of hand size though there are some exceptions like Michael Jordan and Kawhi Leonard who have huge hands for their height. Therefore, it is safe to say Muggsy Bogues holds the unofficial record for the smallest hands in NBA history considering Bogues stood at only 5’3”. You also have to keep in mind that not everyone who plays in the NBA is measured at the Combine. These days the lottery picks typically opt-out and the lower prospects don't get invited. The smallest hands in history probably belongs to someone who didn't get measured, though it's hard to imagine someone having smaller hands especially width-wise than TJ McConnell.