I am still working on writings of Lodewijk van den Berg (1845-1927) the first academic Dutch scholar who did field work about Islam in Indonesia and wrote quite many books and articles, still before Snouck Hurgronje (only 11 years younger) arrived in the field. Snouck did not like Van den Berg, wrote in a strong way against him, more or less as a 'charlatan' and therefore Van den Berg is not really well known in the academic world.
Van den Berg was in the Indies between 1869-1887, leaving the colony two years before Snouck arrived. He was legal advisor on things Arab and Islamic. He translated a major fiqh book and was a consultant for the way how to deal as the ruler of the country with Muslim citizens who enjoyed freedom of religion and were allowed to apply several sections of shari'a law.
Perhaps his best known work is the monography on the Arabs of Hadramaut and the migrants from that region to the Malay Archipelago (where they were business people, active in money lending, small trade and sometimes also in religious business).