Shortly after her birth, the family moved from Australia to Canada, where Thomas received her education and trained as a librarian and secretary.

After moving to Toronto, Ontario, Thomas was employed as an assistant librarian by her local university between 1927 and 1928 and later moved back to Sydney after being influenced to do so by her cousin, Allworth and an influential report highly critical of Australian libraries by Ernest Pitt.

Holme in September 1934, the decision was made that Thomas and Edith Allworth, both of whom were honorary librarians, would establish a children's library in Mosman to develop children's interest in literature.

After establishing the library, Thomas began extra activities for local children and communities such as story-hour's, book reviews and weekly chess groups.

After her death, Thomas was cremated with Anglican rites and the children's libraries section of the Library Association of Australia established the Bess Thomas Award to encourage effort and excellence in children's librarianship.