Thomaides was a member of the city council from 2003-2010. In 2010 Thomaides ran against Daniel Guerrero who had been elected Mayor of San Marcos in 2010, by a margin of 42 votes Thomaides served from 2011-2016 on the city council when he ran for mayor again in 2016 against local business owner, Ruben Becerra. In the 2016 December runoff, Thomaides beat Becerra by a margin of 42 votes- the same number he lost by in 2010. During his first year in office, Thomaides was the 6th Texas mayor to join the Mayors National Climate Action Agenda. 