In some parts of Asia, especially Thailand, it can be rude to point at objects or people with the foot, or to sit with the feet pointing directly towards another person. This is related to the fact that some Buddhists see the feet as the physical and metaphorical lowest part of the human body. By this same logic, it can also be seen as rude to step on a Thai coin with one's foot, as this nation's currency typically carries an image of the Thai monarch, and the rudest part of the body shouldn't be applied directly to a respected person's image.
This code of conduct may apply in other parts of Asia as well, so it may be best to err on the side of caution and use the hands to point. In addition to avoiding pointing, the feet shouldn't be put on display by being propped up on a chair in public. Similarly, the head is considered the highest and most sacred part of the body, so touching a Thai person on the head can be seen as disrespectful, especially if the person being touched is a stranger or distant acquaintance.