Interacting with monks in Thailand
You will see the monks in the early morning going on a procession called Pindapata, or Bindabat in Thai (at least I think that's how it's spelled). That is the time  you will want to offer Dana. Approach with the food and they will uncover the alms bowl and let you put the food in.

When approaching a monk you should always put your hands together at about heart level facing forwards and bowing your head so your forehead is parallel with your hands. Here is a link that talks about how to do it with a nice picture with three examples. With monks, do the version shown on the far right: http://www.phuket.com/magazine1/dos.htm

Women aren't allowed to have physical contact with monks and when receiving offerings other than food in their alms bowl in Thailand they will lay out a white cloth for you to set the offering on.

I'll edit more in if I think of anything.