This is one year extension of stay, and you need to have 800K in your bank two months prior and three months after you apply for your first year unless your embassy offers to give you a affidavit letter to confirm your income.
Formally an onward ticket within 30 days is required anyway. This is rarely checked at the immigration, but the issue could be your airline. I’ll suggest you call them and ask if you plan to go without any ticket.