Southeast Asia’s most popular travel circuit spans Vietnam, Cambodia, and Thailand. These three countries frequently appear together on backpacking routes covering Hanoi to Bangkok, digital nomad circuits moving between Saigon and Chiang Mai, and regional tours lasting two to three weeks. The most common question travelers ask is: “Do I need to buy a different SIM card in each country?” The good news is you don’t have to—if you choose the right regional SIM or eSIM that covers all three destinations with seamless connectivity.
I. Three Options for Multi-Country Mobile Access
You have three distinct approaches for staying connected across Southeast Asia, each with different trade-offs.
Regional SIM cards are physical SIMs that work across multiple Southeast Asian countries. These are often sold at airports, online through travel SIM providers, or at specialized telecom shops. They eliminate the need for multiple purchases and registrations.
International eSIMs deliver digital SIM services via QR code with instant activation. They’re ideal for modern smartphones including iPhone XS and newer, Google Pixel 4 and later, and Samsung Galaxy S20 and above. Setup takes minutes without visiting physical stores.
Separate local SIMs in each country offer the cheapest data rates but require swapping cards, registering multiple times with your passport, and managing different numbers. This option suits budget-conscious travelers who don’t mind the extra hassle.
II. Where to Buy Multi-Country SIMs and eSIMs
You can purchase regional coverage before departure or upon arrival, depending on your preference.
1. Online Platforms Before Travel
Airalo offers eSIM regional plans like AsiaLink covering 15+ countries including Vietnam, Cambodia, and Thailand. Plans range from 3-10GB for 15-30 days at $9-25.
Nomad eSIM provides multi-country Southeast Asia coverage with 5GB/30-day plans around $15, supporting eight countries in the region.
SimOptions sells both eSIM and physical SIM cards with regional bundles. Physical cards ship globally, while eSIMs deliver instantly via email with 6-10GB options for 15-30 days at $19-29.
Klook and KKday offer physical SIM cards for airport pickup at Bangkok (BKK), Ho Chi Minh City (SGN), and Phnom Penh (PNH), providing convenient collection points immediately after landing.
2. Airport Kiosks Upon Arrival
Vietnam airports feature Viettel, Mobifone, and Vinaphone kiosks, though most Vietnamese SIMs don’t offer regional roaming. Cambodia’s Smart, Cellcard, and Metfone typically provide Cambodia-only service. Thailand’s AIS, dtac, and TrueMove H offer tourist SIMs with the best roaming options—particularly AIS SIM2Fly, which works across all three countries.
3. Key Features to Consider in Regional Plans
Not all multi-country SIMs are created equal, so evaluate these critical features.
Multi-country support must explicitly include Vietnam, Cambodia, and Thailand—some “Asia” plans skip certain countries. Data allowance should match your trip length and usage patterns, with 5-10GB typically sufficient for two to three weeks of navigation, messaging, and social media. Validity periods of 15 to 30 days align with most multi-country itineraries.
Hotspot and tethering capabilities prove useful for connecting laptops or tablets while working remotely. Network partners determine connection quality—look for plans using strong local carriers like AIS in Thailand, Viettel in Vietnam, and Smart in Cambodia. SMS and call support matters if you need to receive OTP codes for app registrations, though many eSIMs are data-only.
III. Best Regional SIM and eSIM Plans for 2025
These options provide the most reliable coverage across all three countries.
Top eSIM Choices
Airalo AsiaLink delivers 3-10GB for 15-30 days at $9-25, covering Vietnam, Cambodia, Thailand, and 12 additional Asian countries. It’s the most popular choice among digital nomads.
Nomad eSIM offers 5GB for 30 days around $15, supporting eight Southeast Asian countries with straightforward setup and reliable connectivity.
SimOptions provides 6-10GB regional bundles for 15-30 days at $19-29, available as either eSIM or physical card shipped internationally.
Top Physical SIM Options
AIS SIM2Fly (purchased in Thailand or online) is the gold standard for regional travel, offering genuine roaming in Vietnam and Cambodia with strong network partnerships and reliable 4G speeds.
TrueMove Asia Pass works across the region but requires initial activation in Thailand, making it less convenient for travelers landing first in Vietnam or Cambodia.
Viettel Tourist SIM provides excellent Vietnam coverage, but limited or no roaming to neighboring countries—best for Vietnam-only portions of trips.
Smart Traveller SIM from Cambodia stays local-only without roaming capabilities, suitable only if purchased after arriving from other countries.
IV. Roaming Compatibility Across Countries
Understanding which SIMs work across borders helps you choose the right option.
SIMs purchased in Thailand, particularly AIS SIM2Fly and select TrueMove plans, successfully roam in both Vietnam and Cambodia with data connectivity. Thai tourist SIMs offer the best cross-border compatibility in Southeast Asia.
SIMs purchased in Vietnam rarely work outside the country—Viettel, Mobifone, and Vinaphone focus primarily on domestic service with limited regional roaming.
SIMs purchased in Cambodia typically lock to Cambodia-only service without roaming to Thailand or Vietnam, requiring new purchases when crossing borders.
The best overall roaming SIM remains AIS SIM2Fly, while the best eSIM bundle is Airalo AsiaLink for comprehensive coverage without physical cards.
V. Comparing eSIM Versus Local SIM Cards
Each approach has distinct advantages depending on your travel style and needs.
eSIMs from Cambodiaesim.com provide true multi-country support with instant setup that requires no store visits. However, they’re typically data-only without phone numbers or SMS capabilities, and cost slightly more per gigabyte than local options.
Local SIMs from AIS, Viettel, or Smart mostly cover single countries, require visiting stores or airport kiosks, but provide actual phone numbers with SMS support. They’re more affordable per country but less convenient for multi-destination travel.
eSIMs excel for travelers frequently changing countries who value convenience over cost. Local SIMs work better for those staying longer in each location who need phone numbers for local app registrations.
VI. FAQs
Can I buy one SIM for all three countries?
Yes, regional SIMs like AIS SIM2Fly or eSIM plans from Airalo AsiaLink cover Vietnam, Cambodia, and Thailand with a single purchase and activation.
Can I use hotspot features?
Yes, most regional SIMs and eSIMs allow tethering to share data with laptops, tablets, or travel companions’ devices.
Is 5G available in these countries?
Yes, major cities like Bangkok, Phnom Penh, and Ho Chi Minh City offer 5G coverage, though most tourist SIMs default to reliable 4G LTE networks that provide sufficient speeds for travel needs.