Abang Hashim’s career in the Judicial and Legal Service began on 1 August 1983 when he was appointed as a magistrate in Miri, Sarawak. In the same year, he also served in the magistrates' court of Limbang before being transferred to the equivalent court in his hometown of Sibu in the 1984. In 1989, Abang Hashim crossed to serve in the SarawakLegal Aid Bureau. Nevertheless, he was to return to the judicial service the following year having being made a Sessions Court judge at the national capital of Kuala Lumpur. In the following years between 1992 and 1994, Abang Hashim took the opportunity to join various government departments in his service including serving as the Legal Advisor of the Fisheries Department in the Malaysian Ministry of Agriculture. This was then followed with tenures in various divisions of the Attorney General’s Chambers concluding in 2000 at which time he had become head of the Commercial Crime Unit in the Prosecution Division based in Malaysia's administrative capital of Putrajaya. Upon leaving the AGC, Abang Hashim was then appointed as the chairman of the Department of Cooperative Development Malaysia Tribunal for a period of one year. This was quickly followed by a position as the Head of Prosecution Unit/Deputy Public Prosecutor in the Central Bank of Malaysia. Two years later, Abang Hashim returned to the AGC and resumed his previous posting as the Head of the Commercial Crime Unit from the year 2003 until 2004. In 2004, he was seconded to the Securities Commission Malaysia, Bukit Kiara as its Director of Enforcement Division until 2007. On 1 March 2007, Abang Hashim was appointed as a judicial commissioner. In the same year, he was also appointed as the chairman of the Appeal Board, Board of Engineers Malaysia. As judicial commissioner, Abang Hashim served at the High Courts of Shah Alam, Selangor from 1 March 2007 until 31 April 2009 before being transferred to Kuala Lumpur High Court on 1 May 2009. On 14 October 2009, Abang Hashim was confirmed as a full High Court judge and continued to serve in Kuala Lumpur until the end of 2012. He would then be transferred to serve in the High Court in Penang in 2013. On 30 September 2013, Abang Hashim was elevated as a judge of the Court of Appeal of Malaysia. On 26 November 2018, Abang Hashim was elevated to Malaysia's apex court and took office as a Federal Court judge. As senior most judge from East Malaysia in the Federal Court, Abang Hashim was appointed as David Wong Dak Wah's successor in an acting capacity as CJSS on 20 February 2020. On 25 February 2020, he received the instrument of appointment from the Yang di-Pertuan Agong at the Istana Negara to permanently ascend to Malaysia's fourth highest judicial office.
