The final years of his life were largely taken up with surveying properties on the road from Cape Town to Simonstown. In 1811 a special commission was appointed to determine the extent of land around Cape Town which was not in private hands and therefore regarded as "disposable" by the Government. This led to beacons and boundaries frequently being moved by the Commission over the objections raised by Thibault. His health rapidly deteriorated during this time and he died on 15 November 1815 of pneumonia, believed by his widow to have been brought on by his working in the cold and wet. He was buried in the Somerset graveyard, at a point now under the lower part of the Buitengracht.