Apparently, แอร๊ย (and extended versions such as แอร๊ยยยยยย) is an onomatopoeia of sorts that expresses blushing (https://www.dek-d.com/board/view/1560769/). But I can't figure out how it's supposed to be pronounced. My best guess is that อ is just for the middle consonant class so it can take the mai tri, and it's something like "rae~~~y" with a high tone.

You can hear it, with the accompanying hand gesture, at the start of this video clip:

Sent from my Nexus 5X using Thaivisa Connect mobile app

Typical, no sound in spite of same mobile app.
I "Googled" and found that old foggies like me like to thing that since it is kid's talk (มาเร็วไปเร็ว) we are only going to read it so it doesn't matter. It is supposed to show embarrasment which has no sound, so not onomatopoea.
Is it อ + แร้ย , (new vowel) impossible fo me to transliterate and interestingly, I didn't find any attempt at transliteration in Google.


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Thanks for the video clip; that's not how I expected it to sound at all :)

 

And yeah, it's not really onomatopoeia... apparently, the term for these types of words is "ideophone". I'm getting kinda old myself and wasn't expecting to see/hear teen slang, but someone on another forum said "แอร๊ ;; _ ;;" in a reply to me (without the ย), and I stared at it for a good long while, trying to figure out what the heck it was supposed to mean :)