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.