could use improvement
i liked the riff you set up, it stands on it's own pretty well. you could set a drum rythm in the background though. they have those online if you need one. however, if your going for thrash, your not there yet listen to some early Motorhead, early Slayer, early Megadeth, early Metallica, and maybe some early Anthrax. that's real thrash metal.
in other words, you're not thrashing HARD enough, your going to slow. don't be afraid to play lightning fast on your guitar. it's not a fragile piece of glass, its a muscle, it's strong enough to take such a beating. that tapping part you did was pretty cool though.
listen to raining blood (Slayer), Mermaider and Laser cannon death sentance (by dethklok), metal militia (metallica), and these motorhead songs; Iron fist, Back at the Funny Farm, Ace of Spades, speedfreak, love me like a repitle, and rock out. this should get you on the thrashing mindset
by the way, this sounds like something you recorded in Punk-o-matic 2 or something.