My uderstanding is that gongsi (pinyin for kongsi) were basically shareholder mining cooperatives set up by Chinese immigrants in the mid 19th century, often purchasing a land lease from Indonesian princes. Miners would buy into the company and vote on communal affairs. They were particularly prominent in Borneo but also operated mining leases on the Malay peninsula.

If you have access to an academic library, the following text discusses the quasi-independent mining gongsi of Borneo in comparison with other political forms in the overseas Chinese diaspora:

Blussé J.L. (2002), Kongkoan and Kongsi: Representations of Chinese Identity and Ethnicity in Early Modern Southeast Asia. In: Blussé J.L., Fernández-Armesto F. (Eds.) Shifting Communities and Identity Formation in Early Modern Asia. Leiden: CNWS. 93-106.