Some places allow you to book, not pay, cancel. Can do that print it out. Also I understand sometimes they only care to see you have some place to stay for a few days. You may not need accommodation for the entire time.
The IO are as confused as the rest of us. Sometimes you can, sometimes you cant. I think a difference is A) Do they need fill a visa runner quota, B) Does the tourist look like they're here to spend money (do Thailand some good) or is the tourist a bum. I fall in the middle
I have been here 5+ years - in-and-out, in-and-out every 3 months like a good little habitual tourist. Never an issue. I know it is in part good luck. But the other side of that coin,
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tourist come and a few have issues - does that mean all tourist have issues?