Both the simple form and the -ing form are grammatically correct, so you can't make a grammar mistake. But a speaker might choose one over the other. Read the situation, then decide which form seems better to you in the sentence that contains a verb of perception. Remember that the -ing form gives the idea that an activity is in progress when it is perceived.
Chase
Chasing
Slam
Slamming
Play
Playing
Snore
Snoring
Call
Calling
Walking
Is walking
Calling
Is calling
Play
Playing
Singing ... laughing
Is singing ... laughing
Land
Landing
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