Sometime in the mid-eighteenth century, Soero Pernollo moved to East Java, at the time still a frontier territory contested by the Dutch East India Company, the Mataram Sultanate and the Balinese princely state of Mengwi.[3][4][6] He entered the service of Hendrik Breton, a senior official of the Company. Breton held the post of Resident of Rembang, and was promoted in 1763 to Opperhofd van den Osthoek, or 'High Head of the Eastern Salient', before his eventual elevation in 1768 to the powerful Raad van Indië.[6] Throughout this period, Soero Pernollo was Breton's right-hand man, initially as gezaghebber, or overseer, of three merchant ships, then as harbourmaster of Surabaya, the most important commercial entrepôt in East Java.[6]
During the consolidation of Dutch rule in the Eastern Salient, Soero Pernollo was appointed politiehoofd, or police chief, of Besuki and Panarukan in 1764 with the Javanese noble title of Ngabehi.[3][4][6][7] In this capacity, he played an important role as a source of military intelligence for the Company during the Dutch-Blambangan War of 1767 to 1768.[3] It was thanks to his influence that his younger brother, Kapitein Han Bwee Kong, eventually managed to acquire the lease for the districts of Besuki in 1768, and of Panarukan in 1777.[6]