Actually...Oddly enough, reverb is the OPPOSITE of what you would generally want for this effect! What we're used to hearing for this is general dialogue with room noise and reverb, while the "thoughts" are very, very dry with a lot of low-end from close micing. To achieve this, mic the typical dialogue from 18"+. Treat with very light reverb as needed. For the "thoughts" part, mic 3-4". Only add compression and EQ...NO reverb.
If that isn't an opotion (i.e. voice work is already recorded and cannot be recut), you can add reverb to the "thoughts" part, but add ONLY early reflections...No tail and no actual reverb. Careful early reflections can make something sound closer, but tails add distance, where you want the thought process to be closer than the actual dialogue.
Emmett