Nothing is known of Seng's early life. By 1890 he was a gambling tax farmer in the small port of Chanthaburi on the eastern coast of the Gulf of Siam, and had married a local girl, Thongdi. Since the 1820s, the Siamese government had auctioned the right to collect taxes on various goods and services, and allowed the tax farmers to profit by collecting more than their auction bid. Most of the tax farmers were immigrant Chinese, and several became very rich. By the end of the century, government had replaced most of the tax farms by centralized collection, but not those on gambling, opium and liquor. The consumers of these products were mainly Chinese: and government found it efficient to allow Chinese entrepreneurs to collect these dues.