If you apply DTV on Soft Power, you can enroll any soft power routes and choose "unemployed" since you have money from the rent and you dont need to send documents for your income. You can just send your 6 months bank statement above 500,000 baht. You are unemployed and are joining >180 days soft power (Muay Thai/Cooking etc.) It makes sense and easy :)
You dont need a hotel, you can use vietnam arrival stamp on your passport as a proof. Many of my customers applied in vietnam did the same. They may ask for a selfie in Vietnam as well