I've been working here for last 10 months and I can say BKK is the place where you can literally live like a beggar or a king. The reason i say that is because there are many cheap places for food/entertaiment and super expensive places too. So it's up to you.

For example, their street food prices are like ours (assuming RM1 = 10 THB). So if you eat out 3 meals a day, probably cost around 150 THB. Transportation (Taxi, trains) are cheap too. But in the long run, car is also cheaper than us.  Food at shops like 7-11 is around 30-40 baht or MaxValue supermart (50% off all food after 9pm).

Room rentals are heavily depending on area. Sukhumvit areas are super high priced as compared to areas like Ratchada, Ladphrao which you can get a basic 20-30sqm apartments for less than 10000 baht a month. And yea, you would need basic thai to live in those places as most of them don't speak english.