The Grand Palace is a feast for the eyes. I suggest arriving at 8:30 am when the gates open. You will not only beat the heat, but also the worst of the crowds. I also suggest stopping at one of the two coffee shops they are located at the entrance and exit. They have a wonderful iced Thai tea and a very refreshing honey lime juice that is perfect after walking in the heat. Make sure you are properly attired nothing above the knee and no bare shoulders ( men and women).