In spite of his late start, Mon, who had represented Kerala and Services in his career earlier, pulled a surprise by surging ahead of his fellow competitors in the last few metres to finish first at G M C Balayogi Stadium.
There was light rain just before the men's 100m final but it did not deter the spirit of the competitors although the cool conditions hampered them from returning their best times.
Karnataka athlete Reena George's switch-over from 400m to 100m proved successful as she capitalised on the absence of big guns like Dutee Chand and Srabani Nanda to win the women's 100m dash in a modest 11.99 secs.
Minutes earlier, 'vaulting doctor' Khyati Vakharia of Karnataka cleared a season best 3.80m to win the women's pole vault. She missed the entire last season due to injury. Training under Olympian John Godina in Phoenix, United States, Khyati said she was happy to win here under overcast conditions.
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D Sreekanth, also of Kerala, took his first major title in men's 110m hurdles by clocking a personal best of 14.54secs.
Triple jumper Shilpa Chacko brought the third gold for Kerala by clearing 13.22m. She was the only jumper among the four participants to leap over 13m.
Earlier in the morning, Gujarat's Babubhai Panocha took his third Inter-state title in men's 20 km walk with a time of 1 hour 31 minutes 26 secs. He had earlier won in 2007 and 2013 besides a bronze medal in the last edition in Chennai.