I once forced myself to live on Baht 40,000 for a month, just for the experience, and this was over a decade ago. As a single man, it was not for me.
Nowadays,I have a very good life on less than Baht 40,00 a month, which does not include discretionary spending like hotels, road trips, holidays. But does include the daily running of a 4 bedroom house and 2 x cars.
Is Baht 20,000 a month doable, probably, but not for me.