Buying an iPhone 6 (outside of US) then use it in US?

So I'll move to Seattle, WA in the next several months. I live in Laos (Next to Thailand, if you wonder where it is).

I'm considering to buy an iPhone 6 Plus here, there's 2 models to choose ( Official unlocked US iPhone and official unlocked Thailand iPhone).

I wonder if I buy the US iPhone here and use it in US, will it work perfectly? I'm not sure if I buy the Thailand's and it will work perfectly there. Pros and cons?

Please explain me through all this, thanks!

If the phone is unlocked, it will work anywhere in the world. However, some Iphones have a thing called "sim lock", which means that it will be locked to the first sim you put in it. So make sure it is an unlocked iphone.

If you're planning to use the iPhone 6 in US, get the US unlocked iPhone 6 which will work in both US and Thailand. I'm sure the Thailand version will have different 4G LTE bands some of which are not supported in US. So get the phone from US and you can use the phone in both Thailand and US. If you need US version iPhone 6 factory unlocked at reasonable price, mail me.