He was actively involved in the timber and shipbuilding industry of the region, and acquired Paarden Island in the Knysna Lagoon, on which he built a sawmill and shipyard.

Charles was born in Stavanger, the fifth son of Arndt Leonard Thesen (26 October 1816 – 24 June 1875), a wealthy and respected man in the town.

In Cape Town, the Swedish-Norwegian consul, Carl Gustaf Åkerberg, told the Thesens about the shortage of cargo ships plying the South African coast.

From February 1872 Charles worked as a clerk for William Anderson & Co in Port Elizabeth, but on his father's death in 1875, he joined and managed the family firm, adding new vessels to their fleet, buying more land and trying oyster farming.

One of Charles' sisters, Blanka Thesen, married Francis William Reitz, president of the Orange Free State.

The vessel Albatros traded along the Southern African coast, sailing to Mauritius on one occasion, taking two months and ten days for the round trip.

The passengers and crew were stranded for three days on Dyer Island before being rescued by local fishermen and then travelling by wagon to Caledon.

Improvements in the road and rail infrastructure, particularly the opening of the George-Knysna railway line in 1928, led to cheaper tariffs for travel by land.