Well, generally you have a good idea, and I wanted to use it myself.
There are two things you should consider with this;
When you change EUR to THB within the Revolut app you generally dont get particularly good exchange rate, as Revolut applies a certain percentage of “fee” on so called “illiquid currencies”. For unknown reason they consider THB illiquid, and apply this fee. This means you are loosing some money to begin with.
When using card in Thailand that has been issued in Europe, such as Revolut, you have a problem, but a problem can be managed if you are careful.
When you will want to use Revolut with THB on your account, you will be asked in many cases if you want to pay with EUR or with THB. Always use THB in this case, as you will be charged a lot more if you were to choose EUR.
Other issue are the ATMs. Just because you have THB on your Revolut account as a currency, doesn’t make your card appear “local” all of a sudden. This is still a European card, and when you try to use it in the ATM, you will still be asked to pay the withdrawal fee of “220 or 250” or whatever it is this days. On top of that Revolut only gives you 200 EUR worth of free withdrawals, so if you go over that, Revolut will charge you extra from their end.
Considering cash is king in asia, Revolut is unfortunately not a particularly great, especially in Thailand. On the other hand, if you plan to use the card in places like hotels, airlines, major retail shops and so on, Revolut will give you a certain peace of mind, knowing what rate exactly you got when you bought THB currency even if it is not the absolute best exchange rate you could potentially get.
What I do is take EUR cash, go to one of the best exchange shops in Bangkok that give you almost Forex rates, and use cash most of the time. If I need to use a credit card, I usually choose to use my own bank Mastercard or Visa, as I have noticed this two companies have better exchange rates for Thailand compared to Revolut.
There are places where Revolut is much better (eg. Singapore, Hong Kong, USA, Korea,…)
I hope this helps.
Have fun !