In 2007, Baah won a football reality show in his home country, Ghana. He received a number of prizes which included cash, car, trip to watch the 2010 FIFA World Cup, and two-week trial at Chelsea FC academy. Chelsea player and Ghanaian international Michael Essien stated that he was very happy with Baah's performance and urged the Club to offer him a contract. Baah later returned to Ghana.
In March 2010, Baah sustained a broken shin in a Premier League match against Hearts of Oak at the Baba Yara Stadium. He underwent surgery at the Komfo Anokye Teaching Hospital in Kumasi. In November 2010, he went to Scotland in order to receive assistance with his rehabilitation at Hearts of Midlothian. On 28 November 2011, Gideon rejoined Asante Kotoko. On 30 November, he played his first match after returning from his long injury layoff for the Asante Kotoko SC Reserves side. On 21 April 2012, Baah played his first league match against Mighty Jets helping Asante Kotoko to a 2-0 victory and scoring in the process. While with Kotoko, Baah captured two Ghana Premier League titles and one Super Cup.
Baah started his spell for FC Honka in a form of a loan from Asante Kotoko FC of the Ghanaian Premier League. On Saturday 13 March 2013, Baah made his Veikkausliiga debut in a 2-0 away loss to 'Turun Palloseura. On 22 March he made his home debut at the Tapiolan Urheilupuisto against local rivals HJK Helsinki. Baah scored the winning goal on 25 March 2013 in a 0-1 victory over FC KooTeePee in the Suomen Cup to take his team through to the next round. Baah was chosen to the Veikkausliiga team of the Month for April, May, June and July. On 3 June 2013 Baah was acknowledged for his performance in the first round of the Veikkausliiga by being named by SuomiFutis website as one of the top 5 best players. He scored his first Veikkausliiga goal on 30 June 2013 against FF Jaro where he scored the opening goal in a 4-2 victory. Baah made his Europa League debut on 18 July 2013 in the 2013–14 UEFA Europa League second qualifying round where they lost 1-3 in the first leg to 2012–13 Ekstraklasa runners up Lech Poznań. On 24 July 2013, Baah signed a 2-year contract with FC Honka. At the end of the 2013 Veikkausliiga season, he was officially selected as the leagues defender of the year and rookie of the year.
Helsingin Jalkapalloklubi
In February 2014 it was announced that Baah had signed a contract to join HJK Helsinki. Upon joining the club he helped HJK qualify for the Europa League group stages in 2014 with a 5-4 aggregate victory over SK Rapid Wien. On 6 November, Baah opened the scoring for HJK in a famous 2-1 victory over Italian side Torino. On the following match day of 27 November Baah once again opened the scoring for HJK in another 2-1 victory over Copenhagen.
On 9 February 2016, it was announced that Baah had signed for American Major League Soccer side, New York Red Bulls. To replace defender Matt Miazga who had recently been transferred to Chelsea F.C.. Baah made his first appearance with the club in 2-0 defeat against Toronto FC on 6 March. Upon recovering from a Week 3 hamstring injury that sidelined him for 6 weeks; Baah was loaned to affiliate club New York Red Bulls II on 1 May. The same day, Baah played 45 minutes for the affiliate side in a 2-0 defeat against Charlotte Independence. He scored his first goal with the club on May 21, 2016 in a 7-0 win over NYCFC. Baah suffered a broken leg in a July match against Portland Timbers, sidelining him for the remainder of 2016. Baah missed the entire 2017 season due to complications during his injury recovery, playing only a few matches late in the year with Red Bulls II.
On 1 February 2018, Baah went on trial with Kazakhstan Premier League side FC Kairat. On 4 April 2018, Kairat announced that Baah had signed for their second team Kairat-A. Baah left Kairat-A on 20 May 2018 by mutual consent having scored once for the club.
FC Honka
On 3 January 2019 it was announced Baah would return to FC Honka.
Shakhter Karagandy
On 24 January 2020, Baah signed for Shakhter Karagandy.
International career
In 2009, he received a call-up to Ghana U20 national team. In October 2015, Baah received his first senior call up to the Ghana national team. He made his debut for Ghana in a 13 October friendly against Canada, coming into the match as a substitute in the 87th minute.
