Moan, 29, had been nigh-on unstoppable in the early exchanges of the World Cup season, his victory at the same venue on Saturday making it three wins from the opening four Nordic combined showdowns.
However Sunday's racing belonged to his 27-year-old countryman Kokslien as he held off the challenge of the fast-finishing Frenchmen Lamy-Chappuis to take the win.
But for a better-timed sprint finish Lamy-Chappuis, who had initially looked to have the better of his rival, could have been celebrating however despite being given the same finishing time of 21.36.7 minutes it was Kokslien's day to remember.
Kokslien had produced an impressive gundersen a day previously to improve from tenth after the ski-jumping to end second behind Moan and he was in strong form again.
The podium was completed by Austria's 35-year-old veteran Mario Stecher who had an impressive day's work while Moan could only finish 21st, 23 seconds back.
Despite finishing second Lamy-Chappuis moved to the head of the overall standings with 355 points, Moan is second with 323 and Bernhard Gruber third with 200.