Which UK internet option should you use: eSIM, Thai roaming, a local SIM or pocket Wi-Fi?

Which UK SIM option is best? For a stay of several days, a data-only eSIM is usually the most convenient, because you install it at home and keep your Thai SIM for OTPs. Thai roaming suits very short trips, a local SIM suits anyone who needs a UK number, and pocket Wi-Fi suits groups sharing one connection.

How do eSIM, roaming, a local SIM and pocket Wi-Fi differ?

All four options work in the UK; they differ in convenience, phone number and extra hardware. The table compares them so you can match one to your trip.

Does AIS, True or dtac roaming work in the UK?

Yes, but each operator's packs and partner networks change, so ask your own provider before you fly. Confirm that the pack includes the United Kingdom, how much data it gives and what happens when the data runs out.

• Keep the Thai SIM in the phone to receive bank and app OTPs.
• Turn off data roaming on the Thai SIM if you use an eSIM, so the phone does not draw data from both.
• Set a data-usage alert so you do not exceed the pack.

Where can you buy a UK SIM, and do you need documents?

Local SIMs are sold in EE, O2, Vodafone and Three shops, convenience stores and airports such as Heathrow (LHR) and Gatwick (LGW). Registration and activation rules differ by seller, so ask in the shop before you pay.

• Your phone must not be carrier-locked, or a UK SIM will not work.
• Buying after landing means finding a shop and queuing while you are still offline.
• A physical SIM replaces your Thai SIM in the tray, so store the Thai SIM safely.

Which UK networks exist, and has 3G been switched off?

The main UK networks are EE, O2 (Virgin Media O2), Vodafone and Three. Vodafone and Three merged into VodafoneThree on 31 May 2025, although both brands are still visible. Ofcom states that all four networks have completed their 3G switch-offs.

• Older phones limited to 3G cannot make calls or use data; check 4G/5G and VoLTE support.
• The country code is +44 and emergency numbers are 999 and 112.
• Rural and mountain areas such as the Scottish Highlands, islands and Eryri (Snowdonia) valleys can lose signal, so download offline maps.

Do you get signal and Wi-Fi on the London Underground?

Transport for London (TfL) says Wi-Fi is available at all Tube stations, but it is linked to UK mobile networks, so visitors on a foreign SIM or eSIM may not be able to connect and should not rely on it. 4G/5G coverage underground is expanding, but some tunnel sections still have no signal.

• Download maps, tickets and bookings before you go underground.
• Tap in and out with the same card or device; tapping itself does not need data.
• Free Wi-Fi is common in hotels, cafés and airports, but treat public networks with care; see the related guide on staying safe on public Wi-Fi.

How do you receive SMS and OTP codes in the UK?

A data-only eSIM has no UK number, so it cannot receive SMS at a +44 number, but the Thai SIM in your phone can still receive texts as long as it has a roaming signal. Some UK services, such as the Trainline rail app and card 3-D Secure checks, may send codes by SMS.

1. 1Keep the Thai SIM on for SMSLeave the Thai SIM able to receive SMS, switch off its data roaming and use the eSIM for data.
2. 2Set up Wi-Fi CallingTurn on Wi-Fi Calling if your operator supports it, so calls and texts to the Thai SIM arrive over Wi-Fi; see the related Wi-Fi calling guide.
3. 3Prepare backup verificationWhere a service allows it, use an authenticator app or email instead of SMS, and save backup codes for key accounts.

Once you have chosen, the guide “Best eSIM for the UK 2026: for visits and for study” compares brands, or you can browse eSIM plans for the UK with the button below.

Lihat paket eSIM untuk Inggris