Thai baht will not buy your ema datshi. Bhutan's currency is the ngultrum (BTN), pegged to the Indian rupee. r/BhutanTravels asks how to convert; the useful answer is: land with some USD, use a town ATM, and keep cash for stalls.
This is money only. Connectivity is SIM and eSIM. The baht trip total is the cost hub.
What we quote in baht — and what we do not
As the Thailand GSA we quote Bhutan Airlines fares in THB. The live economy return is THB 31,869. That number is not an ATM rate in Paro. SDF (USD 100 / night) and the USD 40 visa sit on the same written quote after we convert them. You do not pay the airline in ngultrum.
Cards, ATMs, leftovers
Hotels and some craft shops in Thimphu take Visa / Mastercard. Village lunches and market vegetables are cash. ATMs exist in the two towns; they run out on festival weekends. Banks in Bhutan often will not buy ngultrum back — spend down on the last afternoon.
Indian rupees are widely understood because of the peg; Thai baht notes are a souvenir.
Petty theft is rare; still watch an ATM — see Is Bhutan safe?.
