Money.
While in the cities, larger USD notes are commonly used, in the smaller provincial villages, like where we are in the province, Riel is king. You can't take a $50 USD or $100 USD note, and just break it anywhere here. Provincial shop keepers simply don't keep that kind of money on hand.
What works best for us is, while in the city, Chan changes money into 10,000r notes and brings them to the farm. The specific amount to change has varied, depending on how long we would stay here at the farm. Now that things are more suitable to my style of living (READ: living in comfort), we stay here much more than before. In fact, after a short visit to the city (BTB) in early June to pay bills and shop, we will be back here for the duration of the month. Then, we will repeat that again the following month.