Upnotover

I can certainly confirm that the iService app offers the option to extend the validity in 2 ways. Either "buy validity", THB 8.41 for 90 days for instance, or by topping up credit, Different amounts give different extension periods (I did mistakenly mention THB 50 for 90 days, actually it only in fact extends mine by 30). But whatever method is used, the validity can never exceed 90 days. I tested it a long time ago, bought 180 days for THB 14, result was extended from whatever it was, maybe 10 days, to 90, not 180. Queried it with True and they confirmed that my SIM (30 day Infinite Thailand) cannot ever have over 90 days validity. It is quite possible that not all tourist SIMS are created equal.

I use a Redmi Note 10 Pro which has the exact same options as above and works just fine in Thailand. Hard to imagine a newer/better model wouldn't have at least the same functionality. I also remember the "region dependent" statement in the specs when I bought it, reckon it's a standard Xiaomi cut and paste spec.

They do but when I went to try and top it up (balance is ฿0) I see a message "Unfortunately, you cant currently top up Bolt balance in your location if you have zero or positive balance". I have a card attached to the account but would prefer to use the balance if is was a working option. "but we're working on it", the message goes on to say.

I have the same and yes, the longest you can have validity is 90 days, but that resets every time you top up. So add 50 baht every 85 says or so and your good, And yes, it can be done easily online - use the True iService app on your phone and it's simple. I suspect a True shop could change the SIM and keep the same number and give you something valid for 12 months, was going to try but really its no issue to top up so haven't bothered as of yet.

About 4 hours, including a stop en-route.

I did many such trips, always went to Ban Laem (3CPW+93W จบ.4033 Thep Nimit, Pong Nam Ron District, Chanthaburi 22140). Closer than Poipet i would think. It was some years back but I don't suppose anything much has changed.,

You're talking about an annual extension of stay. Replying to a post talking about the initial 90 day non-O visa. Different things with different requirements.