Standstill + thoughtseize

[Deckerator]

I have a quesrion about the following aspect.

My opponent has a standstill on board.
I wanna play thoughtseize on him
Standstill ability triggers and he draws 3 cards.

now my question what happens next. If he draw a counter can he counter the thoughtseize or does it resolve and he has no chance to counter.

[Herjan]

Yes, he can counter the Seize

[HammafistRoob]

To make things a little more clear hopefully...

When Standstill triggers, and then finishes resolving, both players receive priority again before the spell on the stack (which triggered SS) resolves.