My parents (US Citizens) are visiting us in Bangkok. They are here for 3 weeks now. They entered without a visa which they can be here for 30 days. Last minute they decided to stay for another 2 weeks so they can go visit Vietnam as well.

 

They want to fly to Vietnam for 5 days and then fly back to Thailand before leaving to the US.

 

How do they re-enter Thailand? What kind of Visa if any is needed?

They would get another 30 day visa exempt entry without a problem when they return from Vietnam.

OP, do they have on onward flight (eg bkk to USA) within 30 days of returning to bkk from Vietnam. They will require one for airline.

2 hours ago, ubonjoe said:

They would get another 30 day visa exempt entry without a problem when they return from Vietnam.

That's great thanks!

2 hours ago, DrJack54 said:

OP, do they have on onward flight (eg bkk to USA) within 30 days of returning to bkk from Vietnam. They will require one for airline.

I see, yes they have onward flight from BKK to USA.