He began competing in the national competition for his club P.A.C. Rotterdam. He won every meeting he competed in. He started competing in international meetings around the globe.
Five years later Gaisah was considered as one of the best long jumpers in the world, after jumping 8.34 metres to earn a personal best and a silver medal at the World Championships in Helsinki in 2005, only finishing behind star 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 Cheick Touré's the 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
• 2010 Commonwealth Games - third place
• 2006 IAAF World Athletics Final - fourth place
• 2006 African Championships in Athletics - gold medal
• 2006 Commonwealth Games - gold medal
• 2006 IAAF World Indoor Championships - gold medal
• 2005 IAAF World Athletics Final - fourth place
• 2005 World Championships in Athletics - silver medal
• 2004 IAAF World Athletics Final - first place
• 2004 Olympic Games - sixth place
• 2003 IAAF World Athletics Final - third place
• 2003 World Championships in Athletics - fourth place