Rio is contesting the Northern Angami-I seat in the Kohima district and is up against Congress's Seyievilie Chachu.
Nagaland Deputy Chief Minister and BJP leader Yanthungo Patton cast his vote at Riphyim Old III constituency.
Talking to mediapersons after polling his ballot, Rio exuded confidence that NDPP and BJP will form the government in Nagaland and he will be the fifth chief minister of the state
Meanwhile, stone pelting, blank firing in Bhandari constituency was reported.
Police claimed that the situation is under control.
A total 13.17 lakh voters are registered to exercise their franchise in this election.
In Nagaland, female voters (6,55,144) are more in numbers than the male voters (6,52,938).
Total 11,575 polling officials have been engaged by the election authorities.
(With UNI inputs)