At the age of 43, Hii was appointed titular bishop of Castellum Medianum and auxiliary bishop of the Diocese of Sibu on 25 January 2008, by Pope Benedict XVI.[3] He received his episcopal consecration on 1 May 2008, from Archbishop Salvatore Pennacchio.[4][3] Bishop Dominic Su Haw Chiu and Archbishop John Ha Tiong Hock served as co-consecrators.
Bishop of Sibu
On 24 December 2011, Pope Benedict XVI accepted the resignation of Bishop Dominic Su Haw Chiu of Diocese of Sibu and named Hii to succeed him. Hii was installed as the second bishop of the Diocese of Sibu by his predecessor on 15 February 2012, at the Sacred Heart Cathedral in Sibu.