The short version of the geography
Chiang Mai's airport sits southwest of the Old City, the square moat-ringed centre that most visitors are aiming for. The journey is short enough that the difference between the cheapest and most expensive option is small in absolute terms, which makes this a decision about convenience rather than money.
Where you are staying still matters. The Old City, the riverside, and the Nimmanhaemin area west of the centre are three different destinations, and the bus loops serve them differently.
The city bus
The airport publishes the RTC Chiang Mai City Bus as an airport service with a flat 30 baht fare regardless of distance, operating 24 hours, boarding outside the International Terminal on Floor 1. Two loops run from the airport: an R3 Red Line via Wualai Road, Chiang Mai Gate, the Night Bazaar, Tha Pae Gate, Chang Phuak Gate, Nimmanhaemin and Suan Dok, and an R3 Yellow Line via Far Eastern University, Nimmanhaemin, the Three Kings Monument, Tha Pae Gate, Waroros Market and the Night Bazaar.
Read those two lists and pick by which named stop is closest to your accommodation. Because both are loops, the direction matters for how long you sit on the bus, even though both eventually reach similar places.
The airport taxi counter
The official Airport Taxi counter is at Entrance 1, Main Terminal, Floor 1 in the public area, listed as operating until midnight, with a phone number for the service. The fare is set at the counter as a flat rate rather than run on a meter, which is worth knowing because it inverts the advice that applies in Bangkok.
That flat-rate model is fine here as long as you take it from the counter. Agree the price indoors, at the desk, before you walk out with your bags.
Ride-hailing
Grab has a designated pickup point at the airport: Domestic Passenger Terminal, Building 2, first floor, Gate 14, with GrabCar, GrabSUV and JustGrab available at app rates and the arrangement listed as running until midnight. Having an official pickup point is the useful part, since it removes the usual airport confusion about where the driver can legally stop.
| Option | Suits | What you give up |
|---|---|---|
| RTC City Bus | Light bags, any hour, tight budget | A loop route rather than a direct run |
| Airport taxi counter | Luggage, groups, arriving tired | A higher fare than the bus |
| Grab at Gate 14 | Fixed price in-app, no language gap | Walking to the domestic terminal |
Before you leave the terminal
Know your accommodation's neighbourhood name, not just its address, because that is what determines which bus loop or which side of the moat you want. And if you are landing late, confirm with your guesthouse that someone will be there: the airport's own listed hours end at midnight, and small properties in the Old City lock up.