IN airport-well, to be very precies just OUtside-are Mo-Ex that used to give better rates In the hall where ARL=train dep. from. This is just outside ´territory´ of airport where all banks (any Thai bank has an office there) all give exactly same-low-rates.
But this was all pre-covid (never been back since, but booked yesterday ro arr nov-just after Kratong)
There was the odd report these exchanges have closed -a few weeks ago, but unconfirmed.
Ohterwise there is NO exchange on airportgrounds that does give a good rate. Also no idea about Ayut-not been there since many years. The exch that give really good rates are IN BKK-near BigC/opposite World Trade and some along Silom/Suriwong (but do check rates-not all will). The SuperRich ´chains (green, orange and blue) are best known for this.
IF you ask this you are likely looking at expense-best way to Ayut that way-still cumbersome-is take the free shuttle to Don Muang and train from there (opposite motorway), Next best + much more comfy: taximeter to Mochit=northern Bus terminal, then tourbus.
These general Qs have much more response-usually better informed too-at the best known general forums like tripadvisor-the answer is probably there already dozens of times