In a clash between two former champions, it was Ratchanok who emerged victorious with a 21-17 21-18 scoreline in a matching lasting 42 minutes. It was her fourth win over the former World No. 1 Chinese in 11 meetings. Li had won the India Open in 2012.
Japan's Kento Momota also won his inaugural India Open title after seeing off Denmark's Viktor Axelsen 21-15 21-18 and sprawled on the court after hitting a powerful smash which earned him the title. It was Momota's fourth Super Series title.
"I will have to improve my game. I was okay today. You have to keep improving since all the players in top 8 can beat anybody. From now on, there are three more events left before Olympics qualification. I will just try to give my best, no matter if I become a champion or not at the Rio Games," she said.
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Momota won the BWF Super Series Masters Finals, Indonesia Open and Singapore Open last year.
Three years ago Ratchanok had burst into the international scene when she had reached the finals of the All England Champion and won her first super series title here defeating Germany's Juliane Schenk. She made it a golden year, becoming the youngest singles player ever to win the World Champion.
Ratchanok's tryst with injuries - shoulder and leg - also contributed to her three consecutive loses against Li in 2014.