Rent a condo. Water and electricity bills.Food, fruits, caffee etc. Health and accident insurance for 2 people - Expensive.Sometimes you want to eat farang food, expensiver than thai food. Drinking water, beers, zigarette ( or not)
Sometimes hairdresser. Sometimes need to buy clothes. Movie. Taxi.Visa and visa extensions.Maybe border run or visa run. Tv and mobile telephone costs.Sometimes you want to go home ,visit the family and back.
And many other expenses.
This money not enough for 2 people to continue a dezent life in Thailand.