You need something from an adjacent room.
Its a yellow power, which makes you fiy straight up. Where can you still go before it wears off and you cannot activate it?
In an adjacent room, there's a yellow powerup. Bring it to this room and use it to get on the left side of that spike. From there, fall down transform to the ball and bounce to the coin.
You can manage this one with some careful bouncing, too. There's plenty of room to gain height with the two walls under and across from the coin.