The easiest way to rid a person of head lice is to shave the head, which removes all of the nits. Nowadays there are also chemical treatments, but for reasons of preference, tolerance and cost sometimes shaving the head is the best course of treatment. Short of that, you're left with trying to use a special very fine toothed comb, or a pair of tweezers to painstakingly remove them one by one, hopefully getting them all. Frankly, I think it's somewhat of a fool's errand.
In cultures and societies where people live in a more communal environment - such as a single studio room apartment or traditional one-room Thai house there's naturally more opportunity of sharing something as "catchy" as head lice, but it crosses almost all boundaries, cultures, classes and people.
"Nice," I can hear you saying "but what's the point?"
Walking along a street in Pattaya one day I spotted the couple in the photo above and thought "Oh, isn't that sweet! I haven't seen a public display of affection like that since the afternoon in Bangkok," (Hello, Young Lovers) but as I drew closer I could see the tweezers in the inset and knew immediately that while it was a caring act, it wasn't the romantic episode I'd first thought; this was a hunting expedition. In fairness, she may have been looking for fleas, but her actions were one of someone on a mission, regardless. So, that's your warm and fuzzy Valentine story!
I hope wherever you are and whomever you're with today that you have the feeling of being cared about and wanted by people you care about in return. I am, and it's something I never, never take for granted.
Happy Valentine's Day.