A
It does have a speaker, as long as it's the 3G/4G-enabled version: Samsung Gear S2 Smart Watch | Samsung US
"Once paired with a compatible AndroidTM phone, 3G or 4G standalone capability lets you make calls directly from your wrist – even when your phone isn’t close at hand4 – thanks to a built-in speaker and microphone."
OP, here's another support page to look at.