After winning a paramount chieftainship election, which he ran against Abdi Shangali of Hai, Jackson Kitali of Moshi, Petro Marealle of Vunjo and John Maluma of Rombo, Chief Mareale was inaugurated as chief in January 1952.

Thomas Marealle ruled alongside Chief Mangi Mwitori.

The government abolished the system of chieftainships in 1961, although Marealle, anticipating this, had voluntarily left his post the previous year.

His tenure as Mangi Mkuu was regarded as a golden age, marked by major improvements in education, health, the cooperative movement, and communications in his area.

After working for the United Nations in the field of foreign aid for thirteen years, he retired as a diplomat.