It was founded in 1998 under the name of Phak Ratsadon or Citizen's Party. In its first years, it was dominated by a circle of former Thai Nation Party members around Air Marshal Somboon Rahong. It changed its name to the current version in 2004, and was joined by several defectors from the Democrat Party in January 2005, making it the country's second largest party, measured by the number of members. The new executives included the Democrats' former Secretary General Sanan Kachornprasart, and ex-Vice chairman Anek Laothamatas. In the legislative elections of 6 February 2005, the party won 8.3% of the popular vote and 2 out of 500 seats.
Former Mahachon Party member Nitiphoom Naowarat later successfully contested the Bangkok Senator elections.
The party has colluded with 2 other main opposition parties to boycott the election to make it impossible for another TRT led administration to form. These elections of April 2006 were declared invalid. The new elections planned for October 2006 were canceled due to the September 2006 coup. After Sanan and his son Siriwat Kachornprasart left in 2007, stating that small parties had no chance under Thai electoral law, the party sank into insignificance.
- Apirat Sirinawin (current)
- Sanan Kachornprasart (2005-2007)
- "Mahachon Party: Name change approved", The Nation, retrieved 16 July 2011
- "Yingluck declares five-party coalition", Bangkok Post, 4 July 2011, retrieved 16 July 2011