Mamit, who had been battling nose cancer for a number of years, passed away at his home in Taman Stutong, Tabuan Jaya, at around 12am.
He is survived by his wife, Christine Dawung Narub, and three sons.
Mamit, a four-term MP for Mambong, now known as Puncak Borneo, began his political career in 1999.
The veteran Parti Pesaka Bumiputera Bersatu leader reportedly decided not to stand in the last general election due to health problems.
In a Facebook post, former federal minister Maximus Ongkili conveyed his condolences to the family.
“As I remember him, he was an intelligent man, outspoken and always ready for suggestions,” he said, adding that Mamit was respected by everyone and committed to his work.
“He was also a fighter, and I must say he fought a good battle.
“I will never forget our friendship. May God bless his soul. Rest well now, my friend,” he said.
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