On a tangent, Thai lacks "yes" and "no", and in theory one signals assent by repeating the verb or adjective, with or without a negative modifier.

"Hungry, or?" - "Not hungry" "Take, no?" - "Take"

In practice, people will often grunt for yes, and shake their head and break eye contact for no.

Irish also has no "yes" and "no" also (generally speaking) One has to answer with an affirmative statement. "Do you like tea?" "I do"

"Has mary got the message?" "she has"

"ooh, it's wet outside today" "it is"

"Are you happy?" "I am"

Anecdote warning, but this feels very common to me in "Hibernio-English" as well. I do it a lot when a simple yes/no would suffice, and I notice other people doing the same. I assume it's a construct that translated over from Irish. I must start listening out for native English speakers of different nationalities for comparison :)

Well, "yes" and "no" are (or should be) only a part of a more (logically) complete answer that is usually implied and therefore not mentioned. Derived from your example:

"(Are you) hungry?" - "Yes(, I am hungry)!"/"No(, I am not hungry)!"

I assume that the adverbs "yes" and "no" initially occurred as optional parts of an answer (only to later cast their supplementary part of the answer as the optional one). Curious enough, now when I'm thinking about it, I remember utterances with the usage of "yes" in the questions themselves (especially on some immigrants) - like "Hungry, yes?" I wonder what will this evolve into down the road...

"Yes" is ใช่่ , romanized as chai [1]

"No" is ไม่ , ไม่ใช่ , or เปล่า (mai, mai chai, bplao)

There are many other words that also mean yes/no but those are the direct translations that are used extensively in everyday conversation.

[1] http://www.thai2english.com/dictionary/yes.html [2] http://www.thai2english.com/dictionary/no.html

You clearly speak to different Thai people than me day to day. I have only heard them used to mark pieces of information as being correct or incorrect.

All I can say is that day to day, you must be speaking to different Thais than I am. Chai/mai-chai are only used - again, I must stress, by the 10-50 Thais I speak to in Thai each day - to mean "correct" or "incorrect".

Where in Thailand do you live, and what level of Thai fluency do you have that you're running in to frequent counter-examples?

I've lived in Thailand for 14 years, in Bangkok and now Pak Chong, and speak to Thais everyday. I studied Thai at AUA and then with a private tutor. But that's just my anecdotal experience.

I gave two references to standard Thai, a dictionary and a video teaching basic Thai by native Thai speakers. Both show the Thai words for "yes" and "no". If you have an reference of any kind that indicates there are no words for "yes" and "no" in the Thai language please link to it.

Chinese is the same, actually.

"Do you want an ice cream?" "want"