I've read mobile data coverage is spotty on Koh Phayam.

I plan to use the "free" international roaming my American T-mobile plan includes (Simple Global at "2G speeds"). What networks do they use in Thailand?

They mark the island as covered but I'd like to try and find some more specific accounts of using their service or the networks they roam on.

Tmobile coverage map

  • 1
    Can you link to the T-mobile's 2G simple global program details? Any particular reason why you wouldn't buy a local sim (AIS, True, Dtac, My Cat, etc)? 2G signals in LoS are much more difficult than 5 years ago; 3g/4g is more common now.
    – Jon Grah
    Jan 24 '19 at 9:18
  • Would roam instead of mess with a local SIM since I don't pay extra for it. I think t-mobile might often use 3G/4G networks and throttle to "2G speeds"?
    – Carl
    Jan 25 '19 at 1:37
  • 3
    A local sim is trivially cheap in that part of the world, especially compared to n. american rates. You shouldn't dismiss it out of hand. Jan 25 '19 at 5:16
  • 1
    A local sim in Thailand is $1.50, plus $7 for unlimited internet for a month... and that's 3G/4G, not the "2G speeds" which sound painful.
    – dbkk
    Feb 28 '19 at 11:45
  • Any update on what ended up happening when you came t0 Thailand (Koh phayam or other places)? How did the roaming work out for you.
    – Jon Grah
    May 10 '19 at 5:54

Here's what I found out about T-mobile's free roaming while in Thailand:

  • It was almost always roaming on AIS. (I think there was also some other operator in some areas around Bangkok.)
  • The speed was indeed throttled: the connection would not load all websites well but was enough to occasionally upload a small amount of photos. I even tethered my laptop and made travel bookings successfully on some sites that didn't have mobile versions.
  • AIS works perfectly well all over Koh Phayam, I didn't have any issues with network reliability - those concerns are likely outdated. Electricity was also more abundant that expected though it was sometimes off.

For my purposes of light usage I could save the trouble and couple bucks by not buying a local card.


Difficult to know for sure as nearly every foreigner I've run into uses a local sim, but it likely will be AIS or TrueMove (True or True-H or TrueMove H).

Other than for accepting an SMS or emergency call, you may be better off with a local SIM (50-100 baht [$1.6-$3.2]). It will usually come with some call credit + free internet for a couple of days, possibly a week or so. You can get extra monthly packages for 200+ baht or the "pro second" plan where you pay internet per mb (25 satang per MB) and voice (1.2 satang per second) for local calls (100 satang = 1 baht; 30 THB ≈ 1 USD); no monthly fees.

If you don't have a dual-sim phone, you would need an extra phone for this strategy if you wish to have both sims active at the same time.

edit: after evaluating T-mobile's roaming packages for Thailand, it would seem that you have the "T-Mobile ONE and Simple Choice North America" plan, then your Text and internet is covered (calls are $0.25/min).

tmobile international roaming rates

But those with "other" plans must first sign up for "World Class Service". You get $15.00/MB (fifteen USD per Megabyte). $0.50/SMS (outbound) / domestic plan balance (inbound). Voice calls still $0.25/min.

The coverage area seems to be consistent with AIS/True:

tmobile international thailand map

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