He left school at 14 and worked as a timber-cutter and cane-cutter in North Queensland and for an Ipswich dairy.

He was heavily involved in promoting the agricultural industry in the Northern Territory, and in later years ran a caravan park.

At the advent of self-governance, he was then elected as the Country Liberal Party member for Arnhem in the Northern Territory Legislative Assembly from 1974 until 1977, when he was soundly defeated by future Labor leader Bob Collins.

[4][5][3][6][7][8] An arch-conservative, he claimed in 1970 that the conservative Northern Territory News was "communist propaganda" that was "helping to undermine the spiritual and moral life of Australia", claimed in 1971 that there was "not one Aborigine or part-Aborigine who is suitable to sit in the [Legislative] Council", and in 1973 was the only Country Party MP to vote against legalising nude bathing, declaring that "nudity had led to the fall of the Roman Empire".

His CLP colleague, Hyacinth Tungutalum, the first Indigenous Australian MP in the Assembly, later said "Aborigines in particular should honour Rupert Kentish ... he did a lot for us".