Learn Dutch: Hem wordt het fiche door de croupier geweigerd. - He is refused the chip by the croupier.

This is the core rule of Dutch 'dative passives.' In English, you can turn an indirect object into the subject of a passive sentence ('He is refused a chip'). In Dutch, this is not allowed: the indirect object must remain an object. Therefore, you must use the object pronoun hem, not the subject pronoun hij.

If Hem is the object, what is the actual grammatical subject of this sentence?

The subject is het fiche (the chip). In an active sentence ('The croupier refuses him the chip'), the chip is the direct object. When we make the sentence passive in Dutch, only the direct object can become the new grammatical subject.

Why put Hem at the very beginning of the sentence if it isn't the subject?

Putting Hem first is a way to emphasize it as the main topic of the sentence, similar to how the English sentence starts with 'He'. Because Dutch uses V2 word order (the conjugated verb must be in the second position), starting with Hem forces the subject het fiche to move after the verb wordt.

How can I be sure that the verb wordt belongs to het fiche and not to hem?