Simplify the following text for a Grade 12 native English-speaking person.
Original: In Kargil and the lower Suru Valley ( ie Sanku , Panikhar and south as far as Parkachik ) , the majority of the population are followers of Shi ` a Islam , having converted from Tibetan Buddhism in the 16th century under the direction of Thi-Namgyal .
Simplified: The majority of the people are followers of Shi ` a Islam , having converted from Tibetan Buddhism in the 16th century under the direction of Thi-Namgyal .