"when i use a product recorded in my products and services in kip,"
To repeat: you cannot create a product in another currency?

" when the expense is raised with the bricks i have recorded in my products list at a price of  520 kip "
the amount entered in the Cost box of the P/S set-up screen is in your home currency. So if you enter 520 here, that means USD 520. In any case the Cost box of the P/S set-up screen, is static, and optional, and is used just to populate a purchase form. If you are buying inventory in another currency, I would leave it blank, because there are 2 variables: a) the price the supplier charges you and b) the currency exchange rate for the day