If riftherald die and i play deadbloom predator can I play it on opponent battlefield

No — Rift Herald's Deathknell fixes the destination at your base, and Deadbloom Predator's "you may play me to an occupied enemy battlefield" permission can't override that (FAQ #12361, same logic as #11070).

Deathknell reads "Play a unit from your hand to your base, ignoring its Energy cost," and a specified destination in an effect is a restriction, not a suggestion — restrictions beat permissions. If Deadbloom can't legally enter your base, you simply can't choose it there, so it stays in hand.

Note the trigger belongs to the Rift Herald's controller: only if it's your Herald dying do you get to play the unit at all (and per the private-information rule, you can also just decline).