When the Malayan Emergency ended in 1960, Yuen was transferred to the Bukit Aman Headquarters for his first stint and continued to work with different departments such as the Special Branch, Intelligence and Psychology.

Then eight years later in 1968, as a part of his policing career, he furthered his law enforcement studies in Belfast, Northern Ireland, United Kingdom to learn the tactics that were practiced by the Irish Republican Army so that he can make use of it to sharpen up his weaponry skills in order to fight any encountering communist rebels.

After returning home from the UK two years later in 1970, ACP (later promoted to SAC) Yuen was assigned to Sarawak in East Malaysia for the first time (he only returned 11 years later in 1981 as Sarawak Police Commissioner until 1983, when he retired) whereby strong ideological influence from the North Kalimantan Communist Party (NKCP) increases drastically in the state.

In early 1972, three North Kalimantan Communist Party military commanders were successfully eliminated on a battlefield which took place at the Malaysia-Indonesia border (Sarawak-Kalimantan boundary).

That same year in the month of November, he was promoted and simultaneously appointed as Perak Police Chief replacing his fellow colleague, the late DCP Dato' Khoo Chong Kong (later awarded the title of Tan Sri posthumously) who was assassinated by communist gunmen whilst serving in office.