The contract involves vibrocompaction of the ground as part of the land preparation works for a major expansion of the airport.
Mobilisation has already begun and the main works start imminently for completion by mid-2016.
Keller chief executive Justin Atkinson said: "I am delighted to announce Keller's involvement in such a prestigious development. This contract award reflects both the Group's excellent track record using vibrocompaction in Singapore and extensive experience in similar airport construction projects around the world, including previously at Changi."