As far as I know it’s not possible to get a pop-up at the point in the operator-flow that you are describing. If the particular usage you are describing is crucial to you then you might struggle to get a solution.
However, the good news is that it is possible, and relatively well documented how you can take payment in multiple currencies.
The original guide to adding multi-currency support is here:
https://doc.sambapos.org/doku.php/en/v3/working_with_foreign_currencies
But, you will probably find a few short-comings that can prove frustrating, but there has recently been a lot of work by @emre to really improve the handling of multiple currencies.
You can see my discussion of the challenges of multi-curreny and @emre’s solutions here:
You’ll notice that Emre has released quite a few updates to fix specific issues. At the time of writing, these updates are part of the 5.1.61 beta, which you might need to ask for special permission to access, prior to release.
TIP I am not sure how you operate you business, but I am guessing that the Kip and Bhat are much more changeable currencies than the US Dollar. You’ll see in my article above I discuss why I don’t use my true local currency (the Mexican Peso) as my base currency - instead, I base my prices in Dollars so that I don’t need to constantly change my price list.
But the good news is, SambaPOS can now handle multiple-currencies fantastically