Pointing is a no-no in Thailand. Your Thai friends won’t take offence if you point when joking around, as they will understand that as a foreigner you may point instinctively. However, don’t point at monks or pictures of any of the Royal Family, and as a general rule don’t point at people to make reference to them.
If you need to point (indicate) someone out, instead of extending your finger, bend your hand downwards with your fingers leaning toward the floor and your palm facing upward.