Take the sky train to the last stop, On Nut (E9). Walk out through Exit 3. Hail a cab, and take it to Sukhumvit Soi 99 about 1.5km away. Should cost no more than 35 baht. Walk towards the Pricha Building which is along the main road (Sukhumvit).
Look out for the Levi's Factory Outlet. It's by the side. Jeans as cheap as 550 baht. Yes, it's original. But you'll find better bargains if you love button-fly jeans.