What are words that have the sound seid in it?

You're likely thinking of the sound "seed" as in the word "seed." There aren't many words in English that have that exact sound, but here are some examples:

With the exact "seed" sound:

* seed

* indeed

* bleed

* feed

* heed

* need

* reed

* speed

With a similar sound:

* cede

* proceed

* precede

* succeed

It's important to note that the "seed" sound can vary slightly depending on the surrounding letters and the speaker's accent.