What are the tips for applying for a Visa on Arrival in Thailand during a short layover?

Hello everyone, my first post here and i have an important question for a bit of a complicated situation. (VISA ON ARRIVAL / CONNECTING FLIGHT TIME ISSUE)

I plan to travel to Thailand with my girlfriend at the end of the month. During our stay we plan to visit Cambodia for 2 days and return back to Thailand.

On our flight back from Cambodia (Siem Rep), we are flying to Krabi, but we have 1 stop at BKK airport in Bangkok. The issue here is the connecting flight is 90 mins away from our arrival to BKK.

During this time she needs to apply for another Visa on Arrival and we were wondering if you can share ANY tips for us on how we can make this work so she doesn't miss the flight as i heard queues are very long.

Best regards, Milos