Seers, angels, and talking donkeys

In Scripture, angels sometimes appear to people when they're awake, but at other times in a dream or vision. That raises the question of whether Balaam's encounter with the angel and the talking donkey (Num 22:21-35) was a vision. An additional consideration is Balaam's identity was a seer. If you combine the fact that angelic apparitions sometimes occur in dreams and visions with the additional fact that Balaam was a seer, it may well be the case that his surreal experience was visionary in nature–like the talking eagle in Rev 8:13. 

We wouldn't necessarily need an explicit textual clue that the scene was visionary, since the fact that he was a seer, combined with the fact that angelic apparitions sometimes take place in dreams and visions, already clue the reader to that interpretive option.