Depends what you call a big spender. My old, late, (and very rich) Swedish friend would spend 1500 on a lump of cheese, and think nothing of it! He was a big spender (and a generous guy too).
I used to spend 50,000 to 60,000 on a basic, single lifestyle (20k rent).
To my way of thinking, your standard of living on 20k Baht a month in Thailand would be like being on the dole in the UK (I did that in my younger years).