 In the 2007 Kenyan parliamentary election he was elected to the National Assembly of Kenya to represent the Juja Constituency.He was the Chief Whip of the ruling PNU party in Parliament.In April 2010 he lost the parliamentary seat after a court nullified the 2007 election results of Juja Constituency citing irregularities 

A by-election was subsequently held on 20 September 2010, but Thuo was left third after William Kabogo Gitau (NARC-Kenya) and Alice Wambui of Kenya National Congress.