"Your wallet is taken by whom?"
Translation:Dompetmu diambil siapa?
No, "Siapa yang diambil dompetmu" has incorrect word order. "Di-" verbs in Malay are known as patient focus verbs. These verbs are used similarly to passive voice in English, so the nouns that would normally be the subject and object are swapped. This means that "dompetmu" must come before "diambil", and "siapa" must come after "diambil".
But that is not using the object-focus that we are practicing.
“Siapa yang mengambil dompetmu?” => “Who has taken your wallet?” (With the focus on the subject, “who”).
“Dompetmu diambil siapa?” => “Your wallet was taken by who/whom.” (With the focus on the object, “your wallet”)
Yes, sometimes these object-focus sentences sound unnatural in English. But that’s because it’s a direct translation from Indonesian where it is natural to use object-focus more often.