Samadhi is just becoming aware of the 'witness'...to all experience... There has to always be a 'witness to experience' so whether there are thoughts or no thoughts, there is always the 'witnesser'...
No matter how phenomenal the experience, there is still the 'pure existence(Sat), and awareness of that(chit), producing a state of bliss(ananda). So, therefore bliss is just the recognition that you exist... And because you exist, you can experience all of the phenomenal world..
