Hey @chytry
I just came back from Bangkok last week, so I will give you the very fresh information 
In Thailand there are no ATMs left, that would be free to use. Every ATM charges 200 THB to make a withdrawal, including the Citibank ATMs in Bangkok that used to be free until about August 2016.
I have heard that Aeon ATMS (very rarely you can find them in Bangkok) charge 150 THB instead of the standard 200 THB. But saving 50 THB is a very small saving considering they are difficult to find.
On top of that, you have a currency conversion situation with Revolut, where you have to keep in mind that during the weekends and during the Forex exchange (London) is closed, there is a surcharge on the exchange rate, which means you will be loosing out on exchange unless you are careful with the time difference (Bangkok vs. London).
There is however a nice workaround option to buy THB cheaply in advance. It does however require having Thai Bank account.
If you or your friend have Thai Bank account, you can use Revolut to send THB to that account at the optimal time with the optimal conversion rate, and receive funds to Thai Bank within 3-5 days. After that, you can easily withdraw from ATM locally (with Thai ATM card) without a fee.
This is a solution that works beautifully for me, as I am married to a Thai and travel there extensively. I do realise if you don’t have Thai bank account however, you will not be able to use this “free” service.
In that case, paying the local ATM fee and trying to make withdrawals during Forex opening hours is best.
There are also two other good options for getting a good currency exchange rate.
- cash option (siamexchange.co.th) best rate in Thailand (only one office in Bangkok)
- N26 Black card (but you cannot avoid Thai ATM fee this way so in the end, this option is not really that much better than Revolut.
Combination of Revolut and Thai bank account is still a winner !