Before you start

Your original passport — registration is mandatory under TRC rules
An unlocked phone (check eSIM support if you want to skip the counter)
Cash or card for the SIM and a data package

Step-by-step

1
Pick a network for where you will actually be
Metfone (Viettel) has the widest national coverage and is the one to have if you travel to the provinces. Smart was first to 5G and is popular in Phnom Penh. Cellcard is the third option with competitive data bundles. In the capital all three are fine; outside it, Metfone wins.
OnlineWho: YouMinutes to decideFree
2
Buy and register at an official store
Use an official Metfone, Smart or Cellcard shop or the counters at Phnom Penh International Airport rather than a street kiosk. Staff scan your passport and register the SIM to you — which matters, because a SIM registered to somebody else cannot be recovered if you lose the phone and will fail bank verification.
In personWho: You~15 minSIM from about USD 1–2
3
Add a data package immediately
Raw prepaid credit is poor value; the cheap deals are the monthly data bundles bought in the carrier app or at any phone shop. Cambodian data is among the cheapest in the region — a few dollars buys a generous monthly allowance.
Mobile appWho: You~5 min~USD 3–10/month for a generous bundle
4
Use the number for your bank app before you change anything
Activate your bank app, KHQR and any government portals against this number while you still have the SIM in your hand. Changing a registered number later is a branch visit, not an app setting.
Mobile appWho: You~20 minFree
5
Sort home internet separately
Fibre from Online, SINET or EZECOM is widely available in Phnom Penh apartments and is cheap by any standard. Ask the landlord what is already installed in the unit — retrofitting fibre into an older building can take weeks and needs the owner's consent.
In personWho: You (with your landlord)Days to weeks if not pre-installed~USD 15–30/month for domestic fibre

Documents you’ll need

Original passport (mandatory for registration)
Your phone, unlocked
Cash or card
Cambodian address (for home fibre installation)

Things most newcomers don’t know

TRC rules require every SIM to be tied to an identified holder. Borrowing a friend's registration or buying from a kiosk that registers it to the shop feels harmless until you need to recover a lost number, change a bank OTP destination or prove ownership. Both banks and carriers check the registered identity, and unpicking it later means a branch visit with the original registrant.

Source: Telecommunication Regulator of Cambodia; carrier registration terms

Metfone if you leave the capital, anything if you don't.

Metfone is Viettel's Cambodian operation and has the deepest rural and provincial coverage, which matters the first time you drive to Kampot or Mondulkiri and everyone else's signal disappears. In Phnom Penh itself the difference between the three networks is marginal, so choose on where your weekends will be.

Source: carrier coverage maps / traveller consensus

Data is cheap enough that hotspotting is a legitimate backup for home internet.

Phnom Penh's grid is more reliable than Yangon's but not immune to cuts, and building fibre goes down with the power. A generous mobile bundle on a second network costs a few dollars and turns an outage from a lost workday into an inconvenience. Many remote workers here run exactly this setup deliberately.

Source: community-reported

Ask what internet is already in the unit before you sign the lease.

Fibre is cheap and widespread but installation requires the building owner's cooperation, and older blocks in areas like Toul Tom Poung can be awkward. A flat that already has an active fibre drop is worth real money compared with one where you will spend three weeks negotiating. Add it to the viewing checklist alongside water pressure.

Source: community-reported

Common mistakes to avoid

Buying a SIM registered to the shop rather than to you, then losing access to bank OTPs
Running on raw prepaid credit instead of a cheap monthly data bundle
Letting a prepaid number lapse while travelling and losing it — along with your banking two-factor
Signing a lease without checking whether the unit has an active fibre connection
Assuming a data-only travel eSIM gives you a usable Cambodian number for OTPs

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