After leaving politics in 1945, he dedicated himself as an artist and photographer, where he gave advice on stamp policy and was recognised through exhibitions.

[2][3] In 1933 he was appointed by Josef Hoop to serve as the deputy prime minister of Liechtenstein, succeeding Ludwig Marxer.

Following the Anschluss of Austria, under the initiative of Franz Joseph, the Progressive Citizens' Party and Patriotic Union started negotiations for the formation of a coalition government.

[7] This coalition was designed to avoid political deadlock while there was ongoing threat from Nazi Germany, and more importantly, prevent the German National Movement in Liechtenstein (VDBL) from gaining any seats within the Landtag.

[8][9] As a result of the coalition, Frommelt was succeeded as deputy prime minister by Alois Vogt of the Patriotic Union, but retained his position as president of the Landtag.

[1][10]He played a key role in thwarting the VDBL when they attempted a coup in 1939 by blocking their telephone lines and convincing marchers to stand down.