Can I reenter the U.S with a tourist visa?

Question

I have some friends from Thailand; they are currently in Canada, are travelling to the U.S., already have a VISA, and are wondering if they can leave and reenter the U.S. within that VISA period.

Answer 1

For as long as the visa is multiple entry and they use it with in the visa validity period.**

Answer 2

If they hold a multiple entry visa, and not a single entry visa, they may leave and re-enter the US, but only within the validity of the US. If they do hold a multiple entry visa and leave the US, they cannot re-enter the US if their visa expires before they re-enter the US. However, if they only hold a single entry visa then they are only allowed to enter the US once, as their visa will expire/invalidate upon their exit from the US. They must leave the US before their visa expires, or they may face a ban from entering the US for several years.