I can see that US dollars is the way to go for visa on arrival at the bridge @ Nong Khai, but before I go do the money exchange here in Thailand, I want to know whether it's better to pay for my hotel/guesthouse in dollars, kip, or baht while I stay for a couple days?

If I save by taking in more USD vs exchanging baht for kip on the Lao side, then I'll change out a few thousand more baht here on the Thai side.

The main deal with US dollars is the visa at the bridge, if you are a UK citizen you pay 35 dollars or 1500 baht. Even at the exchange rate as it is now you save around 350 baht by paying in dollars. As for guesthouses and the rest, pay with baht and get kip change, they do not seem to rip you off. Night market down by the river will give you change in baht if you pay in baht.

For guest houses and restaurants it all depends on the the exchange rate the days you are there but there is rarely more than 1-3% difference in price between the three currencies so I wouldn't worry and use whatever is easiest for you.

Sí, Jefe. And thanks too, Prem-R. I've got enough dollars for the VOA, and will use baht for the rest. I was there last in 2011 n just forget some of the details of how I did it. Plus wanting to be up-to-date on the latest info. When I first went there in 2003 there wasn't even an ATM and I was traveling with cash and travelers checks - hilarious, those old days. And back then the baht got a very bad exchange rate - using dollars was key to better pricing.

6k always did it for me. Two TR and 35 usd (incl in 6k). Hotel, beer, food, train, transport

You can pay in Thai baht, both at the Lao border and at the hotel.

I have been doing border runs for years at Nong Khai and always use Thai baht.