Should I bring enough cash to cover the entire trip to Thailand? [closed]

It depends entirely on the reason why you want to take cash:

1. If you have a bank account that charges low fees on international ATM withdrawals and foreign currency payments, you're better off just using your card. Whatever exchange rate you will get for your USD probably won't be better than the rate at the ATM.

2. If your bank doesn't have a low-fee option, I suggest opening a virtual account with Revolut (disclaimer: it's a referral link which gives a small bonus for sign-ups). It's a zero-fee bank card that is available to all European residents without visiting a physical office. You order it through an app, receive it in the mail, and then top it up with your regular card (in EUR/GBP). Revolut is also great because it charges the inter-bank rate for all foreign currency transaction and is usually on-par with Transferwise.

3. If you prefer cash just for the sake of it, then yes, bring as much as you need.

Beyond whatever option you choose I recommend getting at least 200$ in emergency cash. You never know when you might need it.