1)
Why did he say "Atah Hashem"?
1.
Radak: You hear their words, unlike they think.
2)
Why did he say that Hashem laughs at them?
1.
Radak: They do not have strength to do what they intend. This is like one who laughs at and mocks an enemy whom he does not fear.
2.
Malbim: He will annul their intent.
3)
Why did he say that Hashem mocks all Goyim?
1.
Rashi: You, who mock all Goyim, will laugh also at these Resha'im.
2.
Radak: He similarly mocks all nations that deny Him, and annuls their words and intents.
3.
Malbim: He will mock all nations who rejoice that [David,] who fights Hashem's wars against them, will die.
