After a month with his new wife, Sing returned to the trenches in France in August 1917, but was in very poor health due to his battle wounds and the effects of gas poisoning. It is not clear whether he operated as a sniper on the Western Front, but in September 1917, he led a unit in the Battle of Polygon Wood in counter-sniper operations. For this action, he was awarded the Oorlogskruis (Belgian Croix de Guerre) in 1918, and was also recommended for the Military Medal—but never received it. In November 1917, he was confined to hospital again due to problems with his previously wounded leg. In mid-February 1918, he was hospitalised due to a gunshot wound in the back. Sing suffered lung disease from his exposure to gas, and it soon brought his military career to an end.