The feet are the least sacred, so when sitting they should not point at anyone - most Thais sit on the floor with their feet tucked under their bodies behind them. To point, particularly with foot, is extremely insulting.
Avoid touching Thai people, it is too intimate a gesture and an invasion of personal space.
When eating, it is considered very rude to blow your nose or to lick you fingers. The right hand must be used to pick up food eaten with the fingers.