While in Lhasa, Chador Namgyal became very proficient in Buddhism and Tibetan literature, and also became the state astrologer to the Sixth Dalai Lama. During his exile, the Sixth Dalai Lama pleased with the erudition of Chador Namgyal had conferred on his exclusive rights to an estate in Tibet. During this period, the son of Yugthing Yeshe (who had saved Chador and taken him to Tibet) was imprisoned by the Bhutanese in Rabdentse. Tibet intervened in the matter and also prevailed on King Deb of Bhutan to withdraw from Sikkim. Chador Namgyal then returned to Rebdantse and the small forces of Bhutan which remained were forced to withdraw. During this period, Sikkim lost some areas in its south-eastern region since Bhutan had colonized the area.