Yes, the 'y' in 'yield' is definitely pronounced, just as it is pronounced in all other words which begin with a 'y'. Yes, yet, yellow, yesterday... the 'y' is always pronounced. We never drop the 'y' - there is no word pronounced 'eeld', just as there is no word pronounced es, et, ellow or esterday! Frankly, I'm baffled as to why you (and Salome) believe that the 'y' is silent. Bear in mind, though, that initial consonants are often affected by what comes before them. So, if you hear someone say 'They yield', the two 'y' sounds merge together so that you might think that there is only one. Likewise, if you hear 'the yield' this might sound like 'the eeld', if you interpret the 'y' sound as belonging to the end of the 'the' rather than the beginning of 'yield' ( much the same way as 'the egg' - with a linking 'y' - might sound like 'the yegg' and lead people to believe that we sometimes choose to drop the 'y' off the word 'yegg'). Could you send us some examples of where you have heard 'yield' pronounced without the 'y'? This might help us solve the mystery.

Yield is pronunced exactly the same way you would pronounce yes.

https://forvo.com/search/yield/ For any pronunciation doubts check this website it will really help you. Also bare in mind pronunciation among different english countries might vary

so is it "thuh yield" or "thee yield"?

The letter Y in “yield” is a semivowel (IPA /j/), and the vowel immediately after it is IPA /ɪj/ (a diphthong in American English). Note that /j/ and /i/ are almost the same sound — /j/ is considered to be a semivowel, while /i/ is a (syllable nucleus) vowel. However /ɪ/ (as in “ship”) is more neutral and lax than the /i/ (“sheep”). Anyhow, I can assure you that native speakers pronounce the Y, but it sounds too similar to /ɪ/ for you to hear it. Keep listening — as you accustom your ear, you’ll notice how the /j/ (the on-glide) has much more tension in the tongue (which is held up very close to the roof of the mouth). For the /ɪ/, the tension is initial released, and then returned for the second /j/ sound (the off-glide).