In June 1993, Haszaimi enlisted into the
Royal Brunei Armed Forces (RBAF), and after completion of Initial Officer Training, graduated with the rank of
second lieutenant. He became an Infantry Platoon Commander in the Third Battalion,
Royal Brunei Land Force (RBLF), followed by several other appointments, including a Mortar Platoon Commander,
Adjutant, Infantry Company Commander, and
Officer Commanding at the School of Infantry. Moreover, he was an instructor for
non-commissioned officers and
junior commissioned officers at the Training Institute RBAF. During the farewell to Lt. Col. Dan Hauser, the Australian Defence Adviser to Brunei Darussalam, Commander Haszaimi showed his appreciation to his service in upholding cooperation between the two nations. He would be succeeded by
Abdul Razak Abdul Kadir on 1 March 2022. Major General Haszaimi paid
General Andika Perkasa a courtesy visit on 12 May 2022 at
Indonesian National Armed Forces (TNI) Headquarters in Cilangkap,
East Jakarta. On his working visit, he aimed to improve relations between the RBAF and TNI. Later on 24 November, he chaired the 21st ASEAN Chiefs of Army Multilateral Meeting (ACAMM). On 1 March 2022, Haszaimi was finally promoted to
major general and appointed by
Sultan Hassanal Bolkiah to be the 12th Commander of the RBAF during a ceremony held at the
Istana Nurul Iman,
Bandar Seri Begawan. To improve military collaboration between the
Indonesian Army and the RBLF, General
Dudung Abdurachman paid a working visit to Brunei on 13 March 2023. In addition to paying a courtesy call on the commander of the RBLF, General Dudung also visited Major General Haszaimi, and took a tour of the RBAF Museum at
Bolkiah Garrison. ==Personal life==