Can you please give me an exemple of the word เอ่ย used as a particle used in riddles and difficult questions. If you can give me a sentence where it is used this way that would be really useful, thank you.

See a translation

Basically เอ่ย is place behind the wh-question words (what where when why). The purpose is to make the sentence become more softer / Funnier.

Example as below

เมื่อวานไปเดทกับไครมาเอ่ย? (Who did you have a date with yesterday?)

Q: ซุปอะไรเอ่ย มีสารอาหารมากที่สุด
A: ซุปเปอร์มาร์เก็ต

Q: which soup has lots of nutrients?
A: supermarket

The first example is use between friends. เอ่ย was added to make the sentence sounds that the questioner is teasing (sometimes they don't need answer at all)

The second example is a word play riddles. In Thai language
Soup pronounce as sùp which is homophonic word of sùp from supermarket and since supermarket sells food it has lots of nutrients in it. So เอ่ย is use in this kind of riddles to make it sounds funnier.