think + object + to infinitive

Solution 1:

The sentence is correct; the instances of use of this construction abound (ref.).

This use of the verb is according to its plain meaning "have opinion/belief" (OALD)).

be thought to be somebody/something

• He's thought to be one of the richest men in Europe.

Your sentence means that there are people thinking that he is the one to have stollen the money.

The verb pattern for this usage in a paper version of OALD is [VN+to inf]; however, a little note at the entry for this construction tells the reader that [the] "pattern is not usually used unless think is in the passive". Therefore, the title of your sentence is correct on the grounds of mere structure but not of usage, as in normal usage there is no more object (the object becomes the subject in the passive turn). The "usage construction" is therefore as follows.

• Sbjt + be thought + to infinitive

Solution 2:

There's nothing wrong with your sentence, but it lacks an object. He is subject in the passive construction given.

With an object in the active voice it would read something like:

They thought him to have stolen the money

And it would still be good English.