The limit of 50,000 Baht in international transfers is ONLY for people who use WISE to transfer the money and ONLY for people using a bank OTHER THAN Bangkok Bank, Siam Commercial Bank or Kasikorn Bank.
You cannot convert a Visa but if you are on an Extension of Stay it may be possible that when you next apply you can change the reason for your extension. You need to ask your Immigration Office if they will allow this then get their list of requirements.