Why would the bank delete it? It's not in the transaction history that immigration gets. They get a bank statement that shows 800,000. That's all they care about after receiving their extra money to make sure that's all they care about.
If you're talking about inside of Thailand, with an application at immigration, then yes. It's a common practice used by agents to bypass the financial requirements of a retirement visa. They take you to the bank, transfer the required funds into your account, get the letter and bank statement from the bank, then transfer the money out of your account. It's only in there for a few minutes. And then because the bank letter/statement does not show the funds in your account the required amount of time, part of the money you pay to the agent is so the immigration officers look the other way about that.