Hi. Your guess is wrong unfortunately.
What Revolut does is it applies a 1,5% markup on “illiquid” currency like THB under the pretence it is illiquid which is not true as Thailand is the biggest or the second biggest economy in SE Asia.
Not to go into too much detail, Revolut is charging a hefty margin on currencies like THB that might be slightly more difficult to “acquire” than lets say USD.
What happens during the weekend is… Revolut adds an additional 1,5% markup (making it 3% in total) for the purposes of currency markets being closed, and there is a chance Revolut could be loosing money when markets reopen on Monday, and that is the day Revolut buys the actual currency you were spending during the weekend. This weekend markup basically protects them against possible loses.
The way regular bank or credit cards work is that they authorise your card for spending during the weekend and your spending gets “settled” a few days later on a working day with a rate that Visa or Mastercard is able to secure on the “settlement day”. This means, with most of regular bank-issued cards, you will not pay this weekend markup, but at the same time, you don’t know what you will be paying for THB as the charge will be settled at a later date with kind of unknown exchange rate.
Revolut however works differently and the moment you swipe the card, that is the rate that will remain “locked”
For some things one is better than the other. But in most cases you would be loosing money if spending with Revolut in Thailand. Rate is more or less unlikely to fluctuate by 3% over the weekend.
If revolut dropped the “illiquid currency” charge for THB it would be great, at least during the week, but this way, you are basically paying more all the time just in case exchange rate changes significantly.
Unless you have some rip-off bank card, you are better off using that in Thailand.
For places like UK or US and most other parts of the world, that do not fall into “illiquid currency” category, Revolut is still the best because you know exactly that you are getting the best possible rate and that rate will stay the same (no settling delay).