FYI.
Don Muang has no money changer past security on your way out. I flew from Thailand to Bali last week. I brought with me a fist full of Thai Baht hoping to change to USD while waiting for boarding. No money changers, had to exchange in Indonesia. I was told there are money changes before security.
TLDR : Answer Summary
A traveler reported that there are no money changers available past security at Don Muang Airport (DMK) when flying out, specifically for converting Thai Baht to USD. Comments indicate that money changers may exist before security and clarify that there are no services for currency exchange on the departure side. Additionally, others highlighted regulations regarding currency limits when leaving Thailand and expressed skepticism about the exchange rates at airport booths.