Pitchkolan was bypassed in the 2005 MLS SuperDraft and had to wait until the second round of the Supplemental Draft to be selected. Pitchkolan appeared in his first MLS game on May 15, 2005, as a substitute for Carey Talley in a game against the Colorado Rapids. His first goal came a game later on May 22, 2005, in a 5–2 win against Chivas USA. In all, Pitchkolan played in 20 games scoring 3 goals in his first MLS season. In 2006, Pitchkolan featured in only 10 games, all as a substitute, and playing a total of 94 minutes for the first team. A highlight of his season was his stoppage time winner against the Kansas City Wizards on April 23, 2006, in a match that ended 3–2. In 2007, Pitchkolan made the transition to center back, a position he occasionally played in college. He made 16 appearances, 11 as starts, but did not score any goals. In 2008, he played 21 games, starting in nine and scored one goal. He was used as cover for Dallas' veteran defender, Duilio Davino. Aaron was one of three players to be active for all 30 regular season games along with Kenny Cooper and Dominic Oduro. Pitch was left unprotected for the 2008 MLS Expansion Draft, but he was not selected. On April 28, 2009, FC Dallas traded Pitchkolan to the San Jose Earthquakes for a conditional pick in the 2011 MLS SuperDraft, but was later put on waivers on March 4, 2010. He subsequently signed for the Rochester Rhinos of the USSF Division 2 Professional League in April 2010. On February 25, 2011, it was announced that the Puerto Rico Islanders had acquired his rights from the Rhinos. In January 2013, Pitchkolan was signed by Minnesota United FC. With a header to feed Lucas Rodriguez, Pitchkolan recorded the club's first assist on April 20 against FC Edmonton. The next week, he scored his first goal with Minnesota, a game-winner in a 3-2 victory at Atlanta. Pitchkolan scored two goals and contributed one assist in 2013, playing 1,665 minutes with 20 appearances for Minnesota. He was named to the NASL Best XI in 2013 for playing a key role on the defense and was selected to the NASL Team of The Week three times throughout the year. He subsequently signed with the perennial juggernaut On a Bender of the Beaches Adult Soccer League in Fall 2017. Arguably the peak of his career, he immediately slotted into the starting lineup and led the squad to numerous BASL championships, including 2019 Spring 11x11 and 2018 Summer 7x7.
