Before you start

Your original passport — photocopies are not accepted for registration
An unlocked handset, or an eSIM-capable one if you want to land connected
For a fixed line, the building's details and confirmation of which provider serves it

Step-by-step

1
Buy and register a SIM at an official store
AIS, True and dtac all have stores in Pattaya's malls and along the main roads. Staff scan your passport and run a facial-recognition liveness check to confirm you are the holder, which takes about a minute. Buying from an official store rather than a general shop means it is registered correctly the first time. There is a cap on how many SIMs one person may hold per operator.
In personWho: You15 to 30 minutesModest for the SIM plus a data package
2
Add a data package rather than running on credit
Raw prepaid credit is billed at poor rates and disappears fast. The value is in add-on data packages bought through the operator app, at any 7-Eleven or at a top-up machine. A few hundred baht buys a generous month. Do this the same day rather than discovering the credit gone within a week.
Mobile appWho: You5 minutesA few hundred baht for a generous monthly package
3
Ask the building which provider serves it before you sign
Pattaya's condominium stock is generally well cabled, but the building's juristic office often has an arrangement with a single provider and switching may not be possible. Ask at the viewing which provider reaches the unit, and test the actual speed in the room you would use. Ordering a provider that does not serve the building costs you a cancelled installation and a fortnight.
In personWho: YouAsk at the viewingFree to ask
4
Order the fixed line and allow lead time
AIS Fibre, True and 3BB are the main options. Installation typically takes several business days. Contracts are commonly twelve months with an early-termination charge, which matters if your lease is shorter or you go home for part of the year. Many furnished Pattaya rentals already carry a connection in the owner's name — establish whether you take it over or order fresh.
OnlineWho: YouSeveral business daysModest monthly fee, usually on a twelve-month contract
5
Keep a mobile backup if you work to deadlines
Heavy rain and localised flooding take out power and fixed connectivity in parts of the city, and recovery is uneven. A generous data package on a second network plus a phone that tethers costs very little and covers the two or three bad afternoons a year that would otherwise cost you a working day.
Mobile appWho: Remote workersSet up before you need itA second prepaid SIM and package

Documents you’ll need

Original passport (mandatory for SIM registration)
Thai address (for a postpaid plan or a fixed line)
Tenancy agreement for a fixed-line installation

Things most newcomers don’t know

A tourist SIM has a hard expiry and cannot be extended — and by the time it dies you will have linked it to things.

Tourist data packs are generous and cheap and are capped at a fixed number of days, after which the number simply stops. People who arrive on one, settle in, and then lose it two months later have usually already registered it against a banking app, a delivery account and their landlord's contact list. If you are staying beyond a holiday, switch to a standard prepaid SIM in the first weeks, not the third month.

Source: Thai operator tourist SIM terms

The building, not the provider, decides your home internet options.

Pattaya's condominium juristic offices commonly have an arrangement with one fixed-line provider, and the physical cabling settles the question regardless of which brand you prefer. Choosing a plan first and discovering the building cannot take it costs a cancelled installation and a fortnight. Asking the juristic office at the viewing takes ten seconds and removes the problem entirely.

Source: Thai condominium fixed-broadband practice

Registration is in person with your real passport and a face scan.

Thailand enforces SIM registration through the NBTC, and the rules tightened to require original-document checks plus a facial-recognition liveness verification at the counter. Photocopies and remote sign-ups no longer work, and each operator caps how many SIMs one identity may hold. Bring the actual passport and expect a brief selfie-style scan as part of the process.

Source: NBTC SIM registration requirements

Always add a package; plain prepaid credit is the most common way newcomers overpay here.

Pay-as-you-go data billed against raw credit costs several times the package rate for the same usage. The generous deals are the add-on packages, activated in two minutes through the operator app or bought at any convenience store. Thailand's mobile data is genuinely cheap, and the only way to miss that is by never activating a package.

Source: Thai operator pricing structures

Common mistakes to avoid

Bringing a photocopy rather than the original passport to register a SIM
Running on plain prepaid credit instead of activating a data package
Staying long-term on a tourist SIM that has a hard expiry and cannot be topped up beyond it
Ordering a fixed-line provider that does not serve the building and losing the installation slot
Signing a twelve-month internet contract when you go home for six months of the year

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