A US phone number for Thai travellers: the +1 format, SMS codes and keeping your Thai SIM
When you need a US phone number and when data alone is enough, plus keeping Thai bank OTPs, dual-SIM setup, Wi-Fi calling and dialling 911.
תשובה מהירה
- Most tourists do not need a US phone number because chat apps and maps run over internet data, but some services may send an SMS to a +1 number.
- US phone numbers use +1 followed by ten digits, and the emergency number is 911.
- Keep your Thai SIM active for Thai bank OTPs, with data roaming switched off on it.
A US phone number uses +1 followed by ten digits, and most tourists do not need one because calls and chats work through apps over data. You only need a +1 number when a service sends its verification SMS to a US number.
How is a US phone number written and dialled?
A US number has a three-digit area code and a seven-digit local number, ten digits in total, and callers from abroad put +1 in front.
- Format example: +1 212 555 0100, where 212 is the area code (a made-up example)
- Inside the USA, local calls often require dialling all ten digits
- On a phone, hold the 0 key to type the + sign before 1
When might you actually need a US number?
Some US apps and services verify identity by SMS, often sent to a domestic number, but no universal rule can be promised, so read each app's own requirements before you travel.
| מצב | Might SMS be needed? | Alternative |
|---|---|---|
| Public Wi-Fi sign-in portals | Some ask for a code by SMS | Pick a network without a code, or use mobile data |
| Ride-hailing apps such as Uber and Lyft | Sometimes ask to verify a number | Create and verify the account with your Thai number at home if the app allows |
| Restaurant waitlists | Many send a queue text | Book via OpenTable or Resy, or ask staff at the door |
| US banks and local services | Often use domestic numbers | Tourists usually do not need these accounts |
For example, if you mainly use Google Maps, WhatsApp and iMessage, a data-only plan is enough, but if a hotel or shuttle driver may ring an ordinary number, a +1 line is more convenient; alternatively your Thai number can take calls over Wi-Fi calling, subject to your carrier's terms.
What is the difference between data-only and plans with a US number?
A data-only plan provides internet but no phone number, while a plan with a US number gives you a +1 line for calls and SMS, so read the plan details before buying.
יתרונות
- Data-only plans are easy to install before flying and keep your Thai SIM in place
- Chat and app calls over data are enough for most trips
חסרונות
- No +1 number for verification SMS
- Calling ordinary US numbers depends on an app
How can you keep your Thai SIM for bank OTPs?
A dual-SIM phone can keep the Thai SIM for incoming SMS while an eSIM handles data, so Thai bank OTPs still arrive without data roaming on.
- 1Keep the Thai SIM in the phoneIf the phone has one physical slot and one eSIM, leave the Thai SIM in the physical slot
- 2הגדירו את הנתונים הניידים ל-eSIMIn mobile settings, choose the eSIM for cellular data
- 3כבו רומינג נתונים ב-SIM התאילנדיSwitch off data roaming for the Thai line only, and check your carrier's terms for incoming calls and SMS
- 4Test before flyingRequest a test OTP from your banking app to confirm it still arrives before you leave
How do you set up dual SIM on an iPhone or Android?
Most recent phones support one physical SIM together with an eSIM, so a Thai SIM and a US eSIM can run at the same time; label the lines Thai and USA to avoid mix-ups.
- Set the default line for calls and SMS to the Thai SIM and the cellular data line to the eSIM
- Turn off automatic data switching so the Thai line does not use roaming data by accident
- Toggle airplane mode after landing if the eSIM has not picked up a signal
- Check the step-by-step eSIM installation guide if you have never installed one
How do Wi-Fi calling and 911 work for visitors?
Wi-Fi calling lets a phone place calls over Wi-Fi where the carrier and model support it, and the emergency number in the USA is 911, dialled from a phone with network signal.
- Set up Wi-Fi calling at home and check your carrier's terms first; see the guide on setting up Wi-Fi calling abroad
- Dial 911 without a country code, and give your address or a landmark clearly
- Parks may have no signal, so tell someone your route before you set out
How do mobile data and a phone number fit together on a USA trip?
WhatsApp, iMessage and maps run over data, and Americans use SMS and iMessage heavily, so data alone covers contact with hotels, guides and friends in most cases.
Common questions about US phone numbers
שאלות נפוצות
How many digits is a US phone number?+
A US phone number has ten digits, not counting the +1 country code.
Do I need a US number for a holiday?+
Usually not, since chat and maps use data, but some services may text a +1 number, so read that service's conditions.
Can I get Thai bank OTPs while in the USA?+
Yes, if you keep the Thai SIM in a dual-SIM phone and have checked SMS terms with your carrier, with data roaming off on that SIM.
Do I need a US SIM to call 911?+
You do not need a US SIM, but you do need mobile network signal, which some parks lack.
מקורות
- FCC guide to the 3G phase-out — Federal Communications Commission — 3G phase-out, 18 באוקטובר 2026
- CBP know before you visit — U.S. Customs and Border Protection — Know before you visit, 18 באוקטובר 2026
- City of New York official site — City of New York, 18 באוקטובר 2026
About the author
Bob Kanokphon Thongdee
- Co-founder of eSIMonline.asia
- More than 7 years in online marketing
- Founder of Cojourney Visa and Cojourney Travel
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