That's ok to send for proof of business but the 500k THB must be in a personal bank statement not a business account. You do need to send a letter detailing you are the owner and can work remotely in Thailand.
ChatGPT will sort the contract out for you. There is no minimum income requirement for the DTV, business owners in receipt of dividends have been approved for the DTV.
If you can find work online then you can get a DTV which gives you a 5 year multi entry visa, Must work online only for a non- Thai company. Other option find a Thai company to give you a job and sponsor your non B visa.