DONT in fact, NEVER, touch a local female friend or otherwise, on any part of her body in public, not even her hand. This doesn't mean you can do it straightaway in private. This is gentlemanliness at its best, not only in Thailand, but across Asian countries. It is taboo. While the male ego still prevails over the female in domestic and office situations, the female is respected. Alas, with night life all over the place, this point seems contradictory.