Never give cash to charities in Thailand. You can't even trust the Police here (Tsunami relief funds anyone?)
If you want to donate, ask what material things they need and use the raised cash funds to buy those things.
That way there is at least some level of traceability where the funds went.
The main charity I support in Pattaya is happy to accept donations of rice, other food and necessities which they themselves distribute to the needy, with proof of distribution available if concerned.