On June 20, 2012 the Electoral Commission decided by a majority to red-card Karun Hosakul after finding him guilty of making false accusations defaming rival candidate Tankhun Jitt-itsara and the Democrat Party at campaign rallies in Don Mueang area at Boon-Anant market on June 3, 2011 and Kosum Ruamjai market on June 12, 2011 during the lead-up to the July 2, 2011 general election.
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On May 9, 2013 Supreme Court's Election Cases Division disqualified and imposed a five-year electoral rights ban on Karun Hosakul and ordered the Election Commission to hold a by-election in Bangkok's constituency 12 to replace him.
He served as Member of Parliament for the Bangkok 12th district.