I got a better exchange rate using an ATM, even with 220 Baht charge and my bank fees.(34 Baht to 1 USD.)
Got 35 Baht to 1 USD at a kiosk on the street in Chiang. (They initially offered high 33 Baht, but went to 35 when I exchanged $3000 USD, All pristine bils, except one had a mark on the back. She looked like she wanted to reject the marked one. I said "all or none." She accepted it (is was a small mark).