The payment options available to employees, besides prepayments on airline tickets and rental car, are travel advances (cash up to 75% of to be reimbursed column on the RAT), direct billing (i.e. registration and hotel), using the Corporate Travel Cards, or (combination of) using personal credit cards or cash.
Depending on your specific situation and requirements, you will need to cooperate with an acquirer who will be able to conduct your transactions in different countries and in their respective currencies. This site presents special solutions for your business. With this payment gateway service provider https://travel.maxpay.com/, you can increase your sales by securing all transaction risks.
I’d say that it really depends on your case, but most of the time, you need to pay in different countries and in their respective currencies, and I think that’s what you need to remember. When I was planning a cruise, more info here, I totally forgot about it, and I was in such a hurry the day before the expedition.