you only need a Thai bank to have unlimited top up balance. Without Thai bank account you can still get one but the max balance you can have is 3000 baht.
Per the regulation, the Consulate "cannot" issue a visa for foreign nationals who are not in Consulate's juridiction and who arecurrently in Thailand. All travelers need to obtain a visa before entering Thailand. *If you entered Thailand without a visa, please contact the Immigration Bureau (immigration.go.th) to explore the options in your case*
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