I'm a U.S.citizen and going to Savannakhet Laos this Tuesday. Is it still $35 U.S.dollar to cross into Laos?

And also my wife who is Thai will be going with me, she wants to use her Thai passport to cross into Laos. How much for her?

I'm asking because I want to have the correct amount of U.S.dollars with me because I heard it's cheaper then using Thai baht.

Also if it is $35 is there a charge to cross back into Thailand? Like U.S.dollars or Thai baht?

Correct, $35 for you, and free for your Thai wife. Crossing back, free for both. Note, these are the official charges, don't know if there's a fee of some sort at either end of the bridge, probably not during normal working hours.

Mac

What should my wife bring with her if she is using her Thai passport?

Passport

Thai ID

4X6cm photo

Copy of passport

Anything else?

The wife, just her passport, Thai are visa free for Laos, that is, no visa required. No photo, no Thai ID card, but she's required to carry that anyway, no copy of passport, but that's always a good idea, just in case the original is lost.

You will need the photo for your Lao Visa On Arrival.

Mac

Make sure your USD are nice new clean bills, they are rejecting any old worn/damaged bills. Last time I went over Friendship Bridge from Nong Khai I had some old worn bills (that was all I could get from the bank) and Lao immigration rejected the bills, I had to walk over to a bank and change them for newer bills.

I just cross to day 13/11/2014 $35 U.S. for you , your thai is 40 , 50 to go in and 80 thai bht to come out .

For information purposes, although no visa required for Thai citizens to Laos, there is an expiry date of 30 days from entry in their passport.