Defending a total of 192 for 4, Odisha were given early wickets by the medium-pace pair of Suryakant Pradhan and Deepak Behera.
Das got the key breakthroughs, dismissing top-scorer Pallavkumar Das (34) and Swarupam Purkayastha (0) in the eighth over. He then took three wickets in five balls to leave Assam at 78 for 8 and they lasted only four overs before being bowled out for 110.
In another match, Tripura tripped up badly in a chase of 153 as they finished 147 for 3, five runs short of the target set by Jharkhand.
Rakesh Solanki had hammered a 58-ball 76 at the top of the order to ensure Tripura were favourites, until the second ball of the final over when he was run out. The equation then became 10 off four balls. Kaushal Acharjee and Manisankar Murasingh could only manage four.