Rai eagled the 11th and also claimed five birdies, along with two bogeys, for an overall score of 11-under at the Karen Country Club in Nairobi.
He is up to 38th in the European Tour Race to Dubai rankings.
Staffordshire’s Richard Mansell had earlier missed the cut.
Shrewsbury’s Ashley Chesters finished joint 52nd after a one-over final round, while former Shropshire & Herefordshire junior Oliver Farr did not make the weekend.
South Africa’s Justin Harding, like Rai, produced a final-day 66 to claim his first win in two years, in Kenya.
Overnight leader Harding kept his composure amid a steady challenge from American Kurt Kitayama to finish 21-under. Scotland’s Connor Syme was third ahead of Spaniard Sebastian Garcia Rodriguez.