[1] His older brother Said bin Ahmad was elected Imam when his father died in December 1783.
A small number of dissident leaders elected him Imam at Al-Masna'ah, on the Batinah coast.
To avoid family disputes, at a meeting in Barka he confirmed his brother Said as Imam in Rustaq, and he ceded control of Sohar to Qais bin Ahmad.
[4] In 1800, Oman suffered from an invasion by Wahhabis from the north, who occupied the Buraimi oasis and besieged Qais bin Ahmad in Sohar.
Early in 1805 he joined forces with his younger brother Mohammed and marched down the coast to Muttrah, which he took with little opposition.
Qais refused since he had growing support and was confident of success, and continued to besiege Muscat.
Qais agree to lift the siege in return for being given Al Khaburah and part of the Batinah.
[6] In May 1808 Qais bin Ahmad was killed at Khor Fakkan in a battle with Shaikh Sultan Al-Qasimi of Ras Al Khaimah/Sharjah.