Dear luong t. n.
Thank you for contacting us.
We would like to inform you that the 300 THB mentioned by our staff is the early check-in fee,
applicable if you wish to check in before the standard time.
As for the 200 THB that was returned to you at check-out, that amount was a deposit for the key cards,
100 THB per card for the two cards you received.
Thank you for your understanding.
Kind regards,
Bangkok City Hotel