i just don’t think your plan of renouncing —> stateless —> apply to be Thai plan is safe or realistic. Any lawyer would agree. There are pathways to Thai citizenship now that are easier than before apparently (thaicitizenship.com), and this would allow you to retain your US citizenship, in case you ever needed to go back to visit or wanted to use your social security. Have you thought about starting with a DTV on your US passport and giving Thailand a try for few years before making any big decision?
I wouldn't give up on DTV if you think Thailand is the best choice for you. Try in Laos, they require an interview which can be used to your advantage. They're mainly concerned about finances, but if you login to your phone and show them you have the $ you're in good shape. You can try Philippines, but I was there for 8 months and it wasn't for me. Wouldn't recommend Manila, go there and try places like Baguio, Tagaytay, Cebu, or even Boracay.
The visa situation is generous and better for those without a Thai DTV, but DTV saves a lot more money than doing continuous tourist visa extensions in Ph. I also got tired of the trips every 60 days to immigration.
Laos will require an interview which will work in your favor if you're worried about the strength of your application. Be prepared to login to your bank account on your phone to show embassy staff in Vientiane, this is apparently how they verify.
It's not in anyone's interest to get one if they have DTV. My understanding is that staying over 180 days and "remitting" money to a Thai bank accounts puts you on the hook for tax liability. I read a post somewhere from someone who consulted Thai attorneys and apparently the current guidance is that if you earn money abroad and keep it in foreign accounts, spend locally with the combination of foreign cards and cash pulled from ATM, you do not have taxable income here.