If you say the words "Hey shy" and drop the "H" then that's pretty much how you'd say "Eisiau"
(I'm from North Wales)
Although in South Wales they're more likely to say "Hey sha" (again without the "H")
The second "i" in eisiau is silent in South Wales, but not in the North.

On this page it gives you two different speakers, the chap says it the North Wales way (proper Welsh!) and the lady says it the South Wales way.
https://forvo.com/word/eisiau/It makes no difference whichever way you say it.
All the best with your Welsh!
Trystan