Jon is the eldest of three sons of the economist Puey Ungphakorn, who was a governor of the Bank of Thailand and rector of Thammasat University, and Margaret née Smith of London.
His brothers are the journalist Peter Mytri Ungphakorn and the political scientist and Marxist activist Giles Ji Ungpakorn.
[1] In 1991, Jon founded the non-governmental organisation AIDS Access, raising awareness for HIV/AIDS in the country, supplying help and training to patients through a network of some 500 local offices.
He worked to include HIV/AIDS patients in the "30-baht-per-visit" national healthcare scheme of the Thaksin Shinawatra government.
He also supported a lawsuit against Bristol-Myers Squibb to allow for a critical anti-HIV drug being produced in Thailand at half the cost.