适合长辈，也适合不爱翻设置菜单的人

Yes, and it is the recommended approach — but have the owner press the buttons themselves at least once while being talked through it, because nobody will be beside them at the other end. Someone who has already opened the cellular settings screen once and already pressed the switch once is far more likely to manage it alone on landing.

It depends on the plan's own terms. Some start counting from the first connection to a network in the destination country; others start on a date set at purchase. We cannot answer for every plan, because the condition varies by provider. The safe route is to read the terms of the one you bought, and if it is still unclear, ask before your travel date rather than after landing.

It is not lost. The original SIM or profile stays exactly where it was; adding an eSIM adds a second line rather than replacing the first. On a handset that runs two lines at once you keep receiving calls and texts on the Thai number as normal. What you should do is turn off data on that line so nothing runs up a charge — and for call and service charges abroad, ask your own operator.

Check three things in order: is aeroplane mode off; is the line selected for data the new one rather than the Thai one; and is data roaming on for that new line. If all three are right and it still will not connect, cycle aeroplane mode once and restart the phone. Every one of those is reversible. Do not delete the profile under any circumstances, and if it still fails, send a screenshot and ask.

There is no standard figure; it is purely a matter of habit. Someone who only messages and takes photos uses far less than someone who video-calls home every night. The most accurate approach is to estimate from the activities that will really happen each day and leave a margin for the days plans change. Many people find a mid-size plan plus hotel Wi-Fi for the long video calls is the balance that works.