Douglas, I'm pretty sure you don't come in on visa on arrival ;) You buy those for 2000baht when you get here, and for people from the 21 countries that do that, I'm 100% sure the rule is 10K baht.
FWIW: I'm also 100% sure the rule is still 10K baht for a visa exempt entry too no matter what the thai immigration officer trys to tell you or show you on a placard.
Here's the actual thai version of the rule they are enforcing.
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