Why did you delete your comment about the rate being 36 to sell and 38 to buy? Of course low populated sex towns like Pattaya have worse rates then Bangkok. But a 1.4% mark up is more than fair, and definitely not the 5%+ you were saying is normal. So the only person wrong... is you :/
I was doing the same thing, I lasted from August 2021 until March 2022 using 30+30 before I got rekt at BKK airport.
I did a month in Indonesia in October, a month in the UK in December for Christmas and 3 weeks in the Philippines in February. When I came back they were adamant it's impossible for a ~20 year old to be travelling like this without working in Thailand because at the airport they're only allowed 2 weeks for a holiday. Eventually they let me in after about 3 hours of back and forth conversation but I wouldn't try to use visa exempt again. For frequent leaving and re-entering the only viable option is the Elite Visa tbh, anything else you'll get pulled up on eventually
One is example is paying an agent for a 1 year volunteer visa disqualifies you from getting the Elite Visa, so if you decide you want to stay long term you'll be forever stuck on dodgy visas until something new comes out
I used VOA's in August, October, December and March. In March they had a problem with it at the airport and said this would be the last time I could get it as it's not meant to be used for people "living" here. I think 2-3 times in a given year is okay but more than that you run the risk of having problems.