This is the expected ritual for the Kings and Queens meeting the Amyrlin - Edit 1
Before modification by Zeratul at 15/12/2010 10:40:26 PM
Egwene mentions this in her POV just before the end of ToM; she expects Elayne to kiss her ring. I realise this is a very trivial matter beside everything else that's going to happen that day, but it bothers me a little. As an Aes Sedai Elayne owes her allegiance to the Amyrlin, but what about her role as a Queen? For the Queen of Andor to show obeisance to the Amyrlin Seat that way seems wrong, and out of character to boot. Elayne is intensely aware of both the importance of appearances and the respect due her as a sitting monarch. I would have expected her to insist on establishing the extent and limits of Egwene's authority over her long since.
As RugbyPlayingAshaman said, the Amyrlin is considered a rank above the Randland monarchs, so the protocol demands that they kiss her ring when meeting her. Here's a confirmation quote from the books:
"TFOH, Ch. 28
“You were the Amyrlin Seat,” he said calmly, “and even a king kisses the Amyrlin’s ring."
This is Gareth Bryne speaking, BTW, so this implies Morgase had done this ritual a few times too.