It's my understanding they're no longer serving as Gurkha/Gorkha formations within the Pakistani Army since the 1956 consolidation of eight old and four new infantry regiments into three large regiments, though some individuals transferred to the then-new Frontier Force Regiment or left for new opportunities in Bangladesh when that country began its War of Independence in 1971. Interestingly, some if not most of the Nepalese hired on for the Bangladeshi conflict were hired through manpower service contractors in Afghanistan....
I’ve never seen anything suggesting Gurkhas serving in Pakistan.I believe the choice back in 1947 was between the Royal Army & the Indian army.