In Laos, cash is still largely handled. Places such as night markets, local stores and even restaurants only accept cash.
ATMs in the city can be found mostly around the Night Market, but sometimes they don’t accept all cards, or accept them only after the fifth or tenth attempt. So it’s worth having at least two cards from different banks, e.g. Visa and Mastercard, so that you don’t have a problem with withdrawing cash.
If you manage to find an ATM that accepts your card, withdraw more money so you don’t have to worry about it later.
At the airport, and border crossings, only cash is accepted, so it’s worth having $40 with you for the visa, as well as $1 for scanning the photo from your passport (if you don’t have prints) and $1 for “service”.
If you don’t have dollars, the airport also accepts Thai Baht, and Euros.
There are also ATMs at the airport (right at the airport exit), and if you don’t have cash, customs officials allow travelers to go out to withdraw it, but here again there may be a problem with withdrawing. So if you have the opportunity, take some cash with you so you don’t have to worry about it.
In Luang Prabang, unfortunately, a few times it happened to us that in stores or markets we were given bad change, so it is worth checking before putting money in your wallet.