Will the Iphone 5s work with straight talk?

So I want to get the new iphone 5s but I'm not sure if it will work with straight talk. Do I have to buy it unlocked? And where can I find the sim card for one of these?

So much as the phone came from a GSM carrier (such as AT&T or T-Mobile) or is factory unlocked and has a clean ESN, it will work with Straight Talk with no real hassle.

You do not need to buy it unlocked, but it doesn't hurt, though.

You can get the needed SIM card from Straight Talk for around $15.