Upvote:2
There is no regular passport control between Belgium and the Netherlands. However, you may be asked to show identification in either country.
In the Netherlands, a residence permit ("vreemdelingendocument") explicitly suffices: https://www.rijksoverheid.nl/onderwerpen/paspoort-en-identiteitskaart/vraag-en-antwoord/met-welke-identiteitsbewijzen-kan-ik-mij-identificeren
I was unable to find anything enumerating the acceptable documents in Belgium, but in general a residence permit is not accepted as an identity document in countries other than the one issuing it. In case a Belgian official is not satisfied with your Netherlands residence permit, you should be prepared to show the receipt indicating that you have left your passport at the embassy for a visa application. This, in combination with your residence permit, ought to suffice.