Seems like a good conversion from Eur to USD.
Did they actually pay him in USD ?
USD is effectively the currency in Cambodia, since the ATMs issue USD and USD are typically used for most transactions of over $1~2.
However, in Laos, with the exception of hotels catering to tourists, most transactions seem to be in Lao Kip and businesses have become reluctant to accept USD. So I imagine he will have to convert it.
However, I did notice some very low spreads on currency conversion when last in Laos in early 2019.