Thom thumbs are a very harsh bit, they say they're a 'shanked snaffle' because of the broken mouth piece, but believe me they aren't, they pinch.
I'd suggest a loose ring snaffle. Very soft, and works on the lips of the horse's mouth. Then you can try moving up to something with a little more leverage. :)
If your horse is past the "snaffle" stage, try using a grazing shank. It has a broken mouth piece, long shanks, and has a mild pressure on the horse's mouth. Very nice bit, and with soft hands, horse responds well. :)
"In the end, they're only going to remember you for the times you smiled when you had every reason to cry."