Well, 4k USD per month is ~130k THB. The purchasing power of the Baht means that that is about equivalent to ~10k USD. (As an example, a can of Coke costs 12 THB in a 7/11).
130k will buy you a lot of luxury in Thailand. You can get a very good condo for 30k per month. You can each out for every meal of every day for about 1.5k per diem, so 45k for food. That still leaves 55k for spending on going out, buying clothes, utilities, gadgets, etc. etc. That is more than "comfortable".
Even 70k per month is more than enough for a very comfortable lifestyle. Local food costs < 100 THB per meal, so you could eat for less than 300 THB per day. A reasonable condo is only 20k if you're willing to live away from the tourist areas.
130k will buy you a lot of luxury in Thailand. You can get a very good condo for 30k per month. You can each out for every meal of every day for about 1.5k per diem, so 45k for food. That still leaves 55k for spending on going out, buying clothes, utilities, gadgets, etc. etc. That is more than "comfortable".
Even 70k per month is more than enough for a very comfortable lifestyle. Local food costs < 100 THB per meal, so you could eat for less than 300 THB per day. A reasonable condo is only 20k if you're willing to live away from the tourist areas.