What you can and what you cannot get away with varies a lot between checkpoints and even individual immigration officers.
Ultimately, you have a decision to make, either play it safe and pay upfront or take your chances and potentially deal with a denied entry.
That's a pretty silly theory, especially when you consider that most overstayers aren't even from the countries mentioned.
Where's that exponential increase in rootless Westerners roughing it out in Thailand illegally? Only in the OP's head.
Those savings come from selling their house, so if and when they return because "Thailand didn't work out" (no income stream, no real plan other than homeschooling the kids), they'll be homeless.
I feel sorry for the kids.
I have yet to see actual evidence that they match passport numbers rather than names. Their announcement was about matching names.
I mean the automatic matching they did. I don't doubt that you'll have to show the same (current) passport to both network provider and bank in case the automatic match failed and you have to visit them.
Indeed, they've been very busy promoting that they are back. I used to be a customer and just re-installed their app to have a look around - my original registration is still valid. I'll give them a try next week.
You'll need to check with each of your banks if they support "cross-border QR code payments" in Laos.
Chances are that some will and others don't (yet). For example, in Vietnam I could already use my Bangkok Bank app for QR code payments, but not my Kasikorn Bank app.
In this case the question is why your passport office didn't cancel your old passport when you picked up the new one. That's what they are supposed to do, unless you qualify for having multiple passports for special reasons.
That's a ridiculous idea. Unenforceable, impractical, doomed to fail miserably.
Maybe some people need to remember that Thailand used to have a very successful HIV prevention campaign. Revive that instead of coming up with comical nonsense.