The incident happened late Saturday in a remote area of the northwestern province of Siem Reap when an 11-year-old boy and six other people went into the well to collect the money. The boy's older sister, Che Chhan, said their father had accidentally dropped the money when collecting water.
She said her 13-year-old sister and 15-year-old brother also died, as well as four of her neighbours.
"My youngest brother thought the amount of money was huge for poor people like us," Che Chhan said by phone.
Police officer Muy Norn said the victims died due to a lack of oxygen at the bottom of the 5-metre-deep well.