this is quoted from official thai embassy in Poland : Proof of finance with the sufficient amont to cover the period of stay in Thailand as follows:
1) 30 euro/person/ day
2) 60 euro/family/ day
Thus, the bank statement of the applicant showing the balance of said amount every month for the last 3 months in English. The bank statement must show account owner.
closing balance of each month is not daily average balance. Those are very different. Its kind of incredible how rules are not specified clearly and how people have different answers for the exact same question