[1] He later joined the Ministry of Finance in the unknown year and served as the director of the central bank and then statistics and economic forecasting on 2 June 1971.
During his tenure, he signed a monetary cooperation agreement between the BEAC member states and France on 23 November 1972 on behalf of the Central African Republic.
[1] When Bokassa received news from René Journiac that Valéry Giscard d'Estaing demanded his resignation from position during his visit to Franceville on 1 August 1979, he was furious and tried to prevent that incident occurred.
Hence, Bokassa tried to lobby some African leaders so that they can defend him from France's overthrow attempt and he entrusted Koyamba to convey this message to Félix Houphouët-Boigny and Léopold Sédar Senghor.
From this secret meeting, he discreetly worked together with Henri Maïdou, Michel Gallin-Douathe, and Bernard Ayandho to remove Bokassa from power.
[1] Koyamba also participated in the Central African Republic's Criminal Court debates where he testified to Bokassa's methods of 20 million CFA state fund corruption.
[1][4] In July 1983, Koyamba was appointed as the Director at the Bank of Central African States (BEAC) Bangui Branch and held that position until 1992.