So I did.
I took the highest rate and the lowest rate. I then took the arbitrary figure of 4,000 GBP to get somewhere near to a 48 Chang lek saving. The difference between high and low (which just happened to be Siam City at the time) and found that was 769 Baht.
I didn't realise I had to calculate over three days from the Friday before the second day and and the number of degrees proof of Beer Chang to the last Sunday after Pentecost and then get your crystal balls out to calculate the rate for next week. And then the kamikhazi comes into the equation. My brain hurts.
I can't get my head round it all. Can you help? Someone is putting 500 Baht into my Bank in Hua Hin. When should I take it out and what ATM should I use?
Can you possibly save me enough for a bottle of Chateau Margaux (preferably 1982 vintage)?
Edited to correct typo.
OK now??
So at the end of it all, it makes no difference whatsoever (apart from a few Baht) which ATM you use.
The exchange rate for cash is similar at the airport to Hua Hin.
It is not advisable to carry more cash with you than you need.
Always check the ATM for hidden cameras and make sure nobody is standing right behind you. A lot of ATM fraud originates in Thailand. We have had at least one thread about it this year.
If it's a Credit Card or Debit Card don't let it out of your site when paying a bill. It's always better to draw the cash from an ATM and pay the restaurant/store in cash.