As in many Asian cultures, the head is considered the most sacred point of the body; the bottom of the feet are the least scared. One should not touch a person’s head nor should one point his or her foot at a person or a scared object., put their feet on tables or chairs and touch anyone with their feet. If you accidentally touch someone with your foot or touch their head, apologize profusely.

Source: http://factsanddetails.com/southeast-asia/Laos/sub5_3b/entry-2952.html