Remove pants. Turn pocket inside out. Place small stone in corner. Tie string around it. Put back on pants. Reach in pocket & pull out string. Put small hole in billfold. Tie string through it. Next roll billfold into string putting it in your front pocket.
Now when they pickpocket they need reach in your pocket and unroll your billfold removing it. Plus pull your pocket out.
A good strong string is best, so they must yank it free.
A rounder midsize coin type purse is best for this as it makes it easy to roll tight to the bottom of your front pants pocket and remove. Keep your cash there.
I normally wear cargo pants with zipper or button down pockets and have no problems.
Or use a money belt, if you have extra cash on you.
Do not let children get too close or surround you. Having some American pennies in your pocket works well: Throw them on the street; the kids will dive for them; you make a fast exit.