[1] He was the son of Jacob Monsen Theiste, a timber trader from Christiania and his second wife, Anna Beata Sørensdatter (née Løchstør).
From 1761 to 1763, he traveled around Norway, financed by the Dano-Norwegian state, during his journey he wrote a detailed journal about the country.
On 29 June 1776, a letter from the King suspended part of his salary, and an appointed commission investigated the complaints and sentenced him to a fine.
Soon after, Theiste sent the Diocesan Governor Christian de Schouboe 40 Danish rigsdaler with a request for a favorable declaration in connection with the complaints received.
In 1780, however, he received the remainder of his salary for the year plus he was awarded an annual pension of 300 Danish rigsdaler because the sentence was deemed to be somewhat strict in relation to the offense.