At the 2008 Summer Olympics, Lalang barely missed running in the finals of the 800 m.
At the 2010 IAAF World Indoor Championships, he won a silver medal in the 800 m.[2] He ran a mile personal best of 3:56.14 at the Drake Relays, defeating training partner and race favourite Bernard Lagat in the process and went on to lower his time to 3:52.18 in Oslo, Norway.[3]
On 29 August 2010 he ran a personal best of 1:42.95 at the Rieti meeting in second place behind the new world record set by David Rudisha.