Another charity I am peripherally involved with and can vouch for as completely legitimate is the Friends of the Asian Elephant, founded by Soraida Salwala, a well-known local elephant activist. Among its projects is the world’s first elephant hospital.
Much of the website is in English, plus there are English-language updates here, including perhaps the hospital’s most famous patient, Motala, who stepped on a landmine while working in logging across the border in Burma in 1999. She was successfully fitted with a prosthetic device.
There is a link on the website to donation information, and you can see that page is here.