Next time do proper research before applying for a visa.
Reading a few Thai visa group would have told the only very few nationalities that can use the income scheme in year, and have to have 800.000 Baht deposited in a Thai bankaccount in year 1 until you can present 12 monthly deposits of more than 65.000 baht.
So you can only blame yourself for not doing resarch before applying.
Just bring your cards, ATM’s are always near by, and it is safer to travel with cards than with cash, except the 20.000 Baht cash, you may be asked to show at Immigration