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His composed second run moved from third equal to first.
Hall took out the title by 0.39s from France's Arthur Bauchet.
He opened with a run of 48.69s before blitzing the field with a 47.42s effort four hours later.
The medal is Hall's second of the Games after securing bronze in the downhill.
Corey Peters also earned a bronze in the sit-ski version of that event.
New Zealand's other Games competitor Carl Murphy's best effort was fifth in snowboarding's banked slalom.
Earlier in the Games, Hall was bestowed with the Whang Yuon Dai award for the male and female paralympian who best exemplify the spirit and values of the event.
It was the first time a New Zealander had won the award.
A 75g pure gold medal will be presented to Hall at tomorrow's closing ceremony.
Organisers said Hall was selected for his passion giving back to the disabled community; encouraging and supporting people into para-sport so they can enjoy the same benefits he has; and to ensure that the future of the Paralympic movement remains strong.