Rule number 1.   You CANNOT spot reduce in one area.

Now, you are already underweight for your height.   So, if you want to lose
the jiggle on the thighs your best bet is to turn to weight lifting.

www.stumptuous.com\weights.html

Start weight lifting.   Work on gaining muscle mass.   Gain some weight in
the form of muscle and you'll see that your thighs will reshape themselves
and you'll lose fat and gain muscle which will make your thighs appear more
shapely.

"Tone" and spot reducing are major falsehoods in the diet world.   They are
terms used for marketing to sell products.   They prey on people's self
images to make you spend money to buy their products.