Not at all, the difference is very distinctive to a native speaker, but I understand how they could sound similar to you.

Maybe search for the 'mimic method' course online, that'll help you with the sounds of English.

They are very different.

Keys is more like KEEEZ with the Z sound at the end and a long E.  It is the same sound as "Be" "Bee" "We"

Kiss has an S sound at the end and has a short I sound.

The vowel in "keys" sounds like the one on the top left of this chart (it looks like "i" and is labelled "front" and "close"): https://en.wikipedia.org/wiki/IPA_vowel_chart_with_audio

The vowel in "kiss" sounds like the one in the chart on the left but in the second row down (shaped like a capital "i", under "near-front" and near-close"). If you have a hard time finding it, this video says "kiss" a bunch of times: https://www.youtube.com/watch?v=gCbs5SLST8g

The "s" at the end of "keys" also sounds like "z". The "s" at the end of "kiss" sounds like "s". You can hear the sounds here (third row down, under "s" and "z") : https://en.wikipedia.org/wiki/IPA_pulmonic_consonant_chart_with_audio

I hope that helps!