I remember seeing a sign in the Songkhla IO stating that no refund will be given, even if an application is rejected.
Undaunted, on my next visit there, I asked a lady officer if I could get back my 1,900 Baht, used for the first extension (expiry date: 29 APR) of my visa-exempt entry.
Even my visa-exempt stamp (expiry date: 30 MAR 2020) became valid after the first free visa-extension was announced and went into effect retroactively on 26 MAR 2020.
Nonetheless, she said No. I simply left it at that and left.