I've been in Bangkok this past week and roaming has been a poor experience. Phone is an iPhone 7 Plus, and I have a high-speed data pass in effect. This same combo had a decent enough experience when I was here 6 months ago. Something has changed.

The phone hops around onto all three networks (AIS, DTAC, True). On True, I have no data or sometimes very slow (as to be unusable) data. AIS is marginally better. DTAC works best but sometimes even trying to force the phone onto DTAC with manual carrier selection results in "No service". Also no matter which network I am on, SMS does not work reliably either inbound or outbound.

Fortunately my phone is unlocked and I bought a local SIM card. I plan to ask TMO to refund at least part of my high speed data pass when I get back.

High-speed data pass probably means no more freebie high-speed roaming promotions.

I wonder whether the data gets a higher priority when using a purchased pass than when they ran the freebie promotion last year. When I used it in Europe last year (UK, Belgium, Germany, Netherlands), the data was usable, but clearly de-prioritized, because T-Mobile probably wasn't paying very much for the roaming data.

Data, like everything else, will continue to come down in price and of course more competition would help.

I just think $20 for 10 days for 1 gb is too much...30 days for 5 gb for $20 is probably a much fairer price.

I'm in Bangkok right now and had the same experience with my iPhone 6s. In the airport it connected to True and went back and forth between 5 bars and "no service."

I couldn't get a quick iMessage to my husband to say that we had landed to send and couldn't connect to uber to get a car so I bought a local SIM. It was cheap and I'm glad I have that option, but that's not the way this is supposed to work. :(

Did you guys try turning off LTE on the iPhone itself?

I didn't. I've been in several countries over the past 6 weeks without needing to mess with the settings.

I was going to use the airport wifi to troubleshoot, but it was asking for my passport number. The True kiosk was right in front of me and I was eager to get to my hotel after an 11-hour flight. It was well worth a few bucks to get reliable data and be on my way.

If I can get something to get my SIM out I'll try turning off the LTE to see if it works.

While I do agree that $20 for 1GB is on the high side, I would (will) pay it for trips of 10 days or less, just for the convenience. Longer than 10 days I'd probably go with a local SIM.

I have a whole collection of (now dead) SIM cards from all over Europe (anybody remember Riiing from Lichtenstein :) ). The only one I kept alive is one from Fonic in Germany -- because that is were I travel the most. Otherwise I've been happy enough with even the throttled T-Mobile speeds -- though I always make sure I have a hotel with decent WiFi.

That's a good thought.

The set of frequency bands for high-speed services in Thailand is a bit of a hodgepodge compared with other countries where I've used my phone. I suspect the issue I was seeing has to do with the phone needing to hop between frequency bands due to this; carriers tweaking their services could play a role in how successful roaming is. The local carriers' iPhone Carrier Settings would be set up to deal with this properly but TMOUS's understandably wouldn't be.

If I get a chance I'll try your suggestion.

You do know you can choose which carrier you use in settings? I just found this out a few weeks ago and the difference between the two was like night and day (iPhone)

Riing....Liechtenstein country code 423...indelibly stamped in my memory bank. Problem was many ld carriers in the USA added ridiculously high surcharges to calls to country code 423 and of course calling out depended on call back.

Did you actually read my entire post?

I had troubles in Thailand last week as well. But when I was there in March and June no issues. Strange.

Thailand is a big problem with tmo - landed at the airport and could not get a connection no matter which carrier I chose (so couldn't use grab.... grrr) Also on my return connection at airport was problematic - strange since their partners are selling local SIMS there which seem to work well- my guess is that tmo roaming doesn't get the best connection/service.
Stayed a month in central Bangkok and had HIGHLY variable service even in the same location with choosing the same carrier. Often had to change carrier to get a decent speed to use google maps (one worked one day another the next in the same location). Since I was there a month in a condo had a lot of opportunity to try same locations (btw tmo tech support was no help and promised call backs never happened :( )

Exactly. I pay $10/GB with my Project FI. Honestly what I'd need to switch back is for the data pass to be <=$10/GB and good for 30 days not just 10 days... or good till you use it up. Either way.

They do that and I'll be back to T-Mo. Till then I'll stick with my Project FI (which I'm on right now enjoying a 15mb/s connection in Trivandrum, India).