No one knows for sure. If gambling were not illegal in Thailand, I would suspect they will probably extend it, or if not, at least give at least some grace period.
The Civil Aviation Authority of Thailand is talking about September for the resumption of flights. Thai had previously said no way they would fly "at least" until August, and that will probably be later now.
Now there have still been limited flights throughout this. But far from normal service and as you allude there would be a big rush. So my money would be on they probably will extend it out at least until there is some semblance of a normal flight situation.
It's possible they won't. Worst case, if they don't and you have to go on overstay, it's 500B/day and is capped at 20,000B. Presuming you surrender at the airport they won't ban you until you overstay for 90 days. So that's really the worst case, and I doubt it would come to that.
Yes technically, legally, they could say no and arrest and throw in prison everyone who isn't out of here on 1 August. But realistically that's not going to happen. It wouldn't happen in normal times, and they realise now is not normal.
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