Before you start

A valid home-country driving licence; for legal driving in your first months, an International Driving Permit (1968 or 1949 Convention) carried alongside it — and crucially with the MOTORCYCLE category endorsed if you intend to ride a scooter (a car-only IDP does not cover two-wheelers).
For a Thai licence: a long-stay basis (Non-Immigrant visa, DTV, retirement/marriage extension, etc.) plus proof of a Chiang Mai address — a Certificate of Residence from Chiang Mai Immigration or your embassy, which in turn relies on your landlord's TM30 address filing.

Step-by-step

1
Get around day-to-day: red songthaews, Grab/Bolt, buses
The red songthaew (rot daeng) is Chiang Mai's signature shared taxi: flag one down, tell the driver your destination, and pay ~30-50 THB per person for short hops around the moat and out to Nimman; agree the price before getting in, as foreigners are sometimes quoted more. Grab and Bolt apps give fixed, transparent fares (a typical Old-City-to-Nimman ride runs roughly 60-100 THB) and remove the haggling and language friction. The RTC city bus covers a few set routes for ~20-30 THB but is infrequent. Tuk-tuks exist but cost more than songthaews and are negotiated.
Mobile appWho: Anyone — no licence, visa, or registration neededImmediateSongthaew ~30-50 THB/hop; Grab/Bolt ~60-150 THB; RTC bus ~20-30 THB
2
Rent a scooter the legal way — licence + helmet, not just a passport
A monthly scooter rental (110-125cc automatic, the default nomad ride) runs about 2,500-3,500 THB; daily rates are ~200-300 THB. Reputable shops take a photocopy of your passport as deposit rather than the physical passport — never surrender your actual passport. Insist on a written rental agreement and basic insurance, and photograph existing scratches before riding off. Legally you must hold a valid motorcycle licence (Thai motorcycle licence, or an IDP with the motorcycle category plus your home licence) and wear a helmet at all times — both rider and passenger. Chiang Mai's hills and rainy-season roads are unforgiving; ride defensively.
In personWho: Renter with a valid motorcycle-class licence/IDP and a helmetSame day~2,500-3,500 THB/month or ~200-300 THB/day; helmet usually included
3
Prepare your Thai-licence paperwork (residence + medical certificate)
To convert at the DLT you need: passport (with visa/extension pages), a Certificate of Residence (from the Chiang Mai Immigration Office near the airport — the old Promenada office relocated — or your embassy; bring your lease and confirm your landlord filed the TM30), a medical certificate from any Thai clinic stating you're fit to drive (issued within ~30 days, ~100-300 THB and a 5-minute visit), your home-country licence and/or IDP, and passport photos. A foreign licence not in English needs a certified translation or an IDP. Photocopy everything; the DLT is strict about a complete file.
In personWho: Applicant, plus landlord's cooperation for the address proofA few days to gather (residence certificate same-day to a few days)Residence certificate ~300-500 THB if via Immigration; medical certificate ~100-300 THB; photos ~50-100 THB
4
Apply at the Chiang Mai DLT — aptitude tests, theory video, licence issued
Book an appointment via the DLT Smart Queue app, then go to the Chiang Mai Provincial Land Transport Office (Hang Dong Road, south of the city). With a valid foreign licence/IDP you can usually convert without the practical road test, but you still complete the physical aptitude checks (colour-blindness, depth perception, reaction/braking reflex) and attend a road-safety theory session/video; foreigners are increasingly asked to pass a short written theory test. Car and motorcycle are issued as separate licences — apply for both if you'll ride and drive. Go early; mornings fill up.
In personWho: Applicant in person at the DLT officeRoughly half a day to a full day on site; same-day issue if your file is complete~205 THB car + ~105 THB motorcycle first licences (2-year), plus small processing fees

Documents you’ll need

Passport with valid long-stay visa/extension (plus photocopies of the photo and visa pages)
Certificate of Residence from Chiang Mai Immigration or your embassy (depends on landlord's TM30 filing)
Medical certificate from a Thai clinic/hospital, issued within ~30 days
Home-country driving licence and/or International Driving Permit (motorcycle category endorsed if applying for the motorcycle licence)
Certified translation of any non-English foreign licence
Passport-style photos (typically 1-1.5 inch)

Things most newcomers don’t know

A car-only IDP or licence does NOT make you legal on a scooter — you need the motorcycle category specifically, and most foreigners don't have it.

Thai police checkpoints near the moat, Nimman, and on roads to Doi Suthep routinely stop foreigners on scooters and fine those without a matching motorcycle licence (~500 THB). The deeper risk is insurance: travel and health insurers deny scooter-accident claims if you were riding unlicensed or without a helmet — and with Thailand's very high road-death rate, that gap can be financially ruinous.

Source: Thailand DLT licence categories (dlt.go.th); U.S. Embassy Thailand driving guidance

Use Grab or Bolt instead of haggling songthaews and tuk-tuks when you're new or it's late.

Red songthaews and tuk-tuks negotiate fares and sometimes quote foreigners more, especially at night; Grab and Bolt show a fixed price up front, track the route, and remove the language barrier — often costing about the same as a fair songthaew fare for a private ride.

Source: Chiang Mai municipal transit / ride-hailing availability

Your Thai licence (and even the residence certificate) hinges on your landlord filing the TM30.

The Certificate of Residence the DLT requires is issued by Immigration only when your address is on file, which depends on the landlord/host submitting the TM30. If that wasn't filed, you'll be sent back to sort it before you can get the certificate — a common, avoidable delay.

Source: Thailand Immigration TM30 requirement; Chiang Mai Immigration Office

Common mistakes to avoid

Riding a scooter on a car-only IDP/licence — illegal, fineable at checkpoints, and voids your accident insurance
Skipping the helmet: it's legally required for rider and passenger, a frequent checkpoint fine, and the single biggest factor in surviving a crash
Handing your physical passport to a rental shop as deposit — give a photocopy; losing leverage over your passport invites disputes over 'damage'
Assuming the IDP is permanent — it expires (often within a year) and lapses with your home licence, so long-stayers must convert to a Thai licence
Treating Chiang Mai roads as easy — wet-season roads, hills toward Doi Suthep, and dense scooter traffic make this genuinely dangerous; ride sober, slow, and defensively

Some of this may be out of date. Spotted something inaccurate? Help us keep it right for the next newcomer.