Most foreigners earns upwards of 50,000 Baht depending on the work you are doing and responsibilities. Using the most common jobs for foreigner wanting to live in Bangkok, which is an English teacher; average pay for a junior English teacher is 35,000 baht and can go up wards to 70,000 depending on your experience and also the school you were able to get into to teach.
Anything above 100,000Baht is consider luxury based on Thai standards and if you see yourself as an expat premium, 100,000 Baht should see you living comfortably in a 1 – 2 bedroom apartment which will cost around 15,000 – 30,000 Baht a month and still able to enjoy decent dining options twice a week and also one or two nights out per week.
Food is extremely affordable in Bangkok if you don’t savor on foreign taste bud and imported ingredients all the time. Prices in places like Big C can be used as the benchmark on your lifestyle here. Mobile and internet is cheap as well. Go with companies like True or AIS and you cant go wrong.
How much you can save depends on your lifestyle. For example, I have found certain imported items here to be more expensive. If you go full “local”, you can save a lot here. If you rent an apartment near the office, you don’t need to worry about transport, and so forth.
For comparison purposes, average Thai salary is about 15,000 Baht per month* and so if you are earning anything above 50,000 Baht and living a Thai life, you should have a pretty decent one.