If one sees thoughts as empty as in absence or a void, then it
is false emptiness.
Thoughts are just conditioned arising - one thought arise is Yuan
Qi, and conditions the other thought to arise and is constantly
changing - ungraspable. These are conditioned dharma and empty of
inherent existence.
Treat thoughts like heart beat, walking, and breathing. For example
when you walk, you do not keep thinking "I want to walk.. i want to
walk..." it is the most natural thing. There is no thoughts, and no
self walking. 
Similarly thoughts are just conditioned phenomena, do not arise
another mind on top of it, just like your heartbeat. Do not make it
an imputed reality out of Fa (dharma/phenomena).
When we do not impute reality, it is mere Pure Awareness, neither
is there seperation of inner and outer.
It is every time when a condition and cause arise, contact is made,
perception arise almost immediately, that is the problem. Therefore
the immediate Buddha Nature is not known.
Think about it - did you first HEAR the sound, or KNOW the
sound?