Our mind is a receiver as well as transmitter. We also have a storehouse of earlier thoughts we have registered. To attain a thoughtless state, we have to first disassociate from our thoughts as "my thoughts". This means letting go of "my ideas", "my beliefs" or anything to do with mine. Instead start observing or witnessing the thoughts just as you watch a cloud passing in the sky. Once you can do this consistently, thoughts have no power over you and it becomes easier to switch of your receiver and reach a 'thought less state'