Later, he joined the Pan-African Union for Social Democracy (UPADS) and was elected as one of the party's vice-presidents in December 2006, at its first extraordinary congress.
He was chosen as the candidate for the Pan-African Union for Social Democracy (UPADS) for the 2009 presidential election.
Joseph Kignoumbi Kia Mboungou was the UPADS presidential candidate in the presidential election held on 10 March 2002; he took second place but received only 2.76% of the vote, with Sassou Nguesso winning by an overwhelming margin according to official results.
His sole rival for the nomination, Joseph Kignoumbi Kia Mboungou (who was the UPADS candidate in the 2002 presidential election), withdrew from the vote, complaining of "lack of transparency in the process", and Poungui, as the only candidate, received about 85% of the vote.