Gaisah moved to the Netherlands in 2001 and currently lives and trains in Rotterdam. He competes for P.A.C. Rotterdam.
In 2005 jumped a personal best 8.34 metres to win the silver medal at the World Championships in Helsinki, finishing behind Dwight Phillips. On February 2, 2006, in Stockholm he leaped to an African indoor record that also won him the gold medal in this event by jumping 8.36 metres. He continued his good form to win the 2006 IAAF World Indoor Championships a month later with a jump of 8.30 metres, followed quickly by the 2006 Commonwealth Games gold medal with a jump of 8.20 metres.
At the 2006 African Championships in Athletics Gaisah won the gold medal with an 8.51 m jump, beating Cheikh Touré's African record of 8.46 metres from 1997, but as the tail wind was too strong (+3.7 m/s) the result could not become a new record. Since July 2013 Gaisah officially competes for the Netherlands after gaining his Dutch passport.