Nobody can estimate the exact chances, but it could go either way.

Where are you now? In your situation, I'd try to enter overland, rather than by air -- in that case, if you're refused, at least you won't be detained (at your cost) and potentially made to book expensive last-minute flights out. If that's impractical, at least prepare for the possibility of being turned away and have a plan B.

If refused, it's better to go to a neighboring country (like Malaysia) and explore your options there (maybe attempt another ground crossing), than to book an expensive last-minute ticket back to your home country right away while in airport detention.

Do carry 20k baht in cash on you, just so that they can't refused you based on not having them.