If you need to withdraw cash from an ATM in Thailand, it depends on which bank card you use. Take the debit card of China Bank as an example. As long as it is outside the country, no matter which ATM machine, a handling fee of 5% will be charged, with a maximum of 2000 yuan per day. If it is a balance inquiry, each inquiry will cost 15 RMB. I suggest you go to the bank where the bank card is located to consult the staff. Every bank and even every card has different rules. Generally speaking, the exchange rate is the real-time exchange rate. There are also cash transactions in Thailand, that is, using RMB cash to buy Thai cash, generally only 100 RMB. It depends on where you change money. Some black markets are cheaper than banks, but the disadvantage is that the group may not be able to get there.
Foreign exchange is usually reserved on the same day and cashed the next day.
By the way, it's best to spend all the Thai baht in Thailand. Bank of China does not accept small amount of Thai baht to RMB, that is, it does not accept other denominations of Thai baht except 1000 paper money.