Seungri: Don't go. (Don't go don't go)
Don't leave. (Don't do it. Don't do it. Don't do it.)
This is unlike you.
Daesung: Remaining far away. In the way love has split.
Translations by @kristinekwak
Fan-made mix of the 3 teasers that were released so far:
Source: Nazuki @ BestizLabels: Monster, Seungri, Still Alive Special Edition, Videos