What should we consider when exchanging currency upon arrival in Thailand on a visa-exempt entry?

We are coming into Thailand for the 3rd time since October on a 30/day visa exempt (USA passport). Since it’s our 3rd visa-exempt entry, making sure we have all the T’s crossed. We are in Seoul right now, taking out Korean Won to the equivalent of 40,000 baht for our family of 4. Will need to exchange at least some into baht at the airport to pay for taxi, but assuming it’s a bad idea to exchange it all at the airport at once? We don’t normally exchange $, and use ATMs in the countries we visit, so not the most experienced getting the best rates.