A friend of mine works in Bangkok pretty regularly, so it ended up cheaper to rent an apartment than get hotels (plus he can leave clothes etc behind.)
A nicely sizes 2 double bed apt is £450 a month all in including utilities - plus a pool and huge roof terrace shared with the other people there - looks great.
If you can get a visa to work there, and have the cash, you can have an amazing life out there for sure.
You can find a condo cheaper and also much more expensive. There's also often a hidden "farang tax" where you will be charged more simply because they know you can pay more, regardless of the quality of the place. This is where the variance comes in. It happens with certain services, especially things like taxis (but not Grab or Line Man).
But yes, Bangkok / Thailand in general has huge wealth disparity. There are a lot of people living on very little money, and some people grossly rich.
Given that Bangkok is the biggest city in the country, I'd expect costs and wages to both be higher than the national average--though probably, to be fair, not _this_ much higher.
Oh yes, this is on the luxury side - but it is a great serviced apartment, on par with a hotel experience. You can definitely get far far cheaper accommodation in Bangkok and throughout Thailand, but if you are bringing a western wage or savings you can live an amazing lifestyle.
I was curious so had a quick look at the average monthly salary in Thailand, which apparently comes to ~350 GBP. Your friend's rental price is humongous.
Thai HN users - what do you all think of this behaviour? What's the price of a nice apartment which doesn't have a pool and huge roof terrace, I wonder?