Summary
If you make 1,670,132 บาท a year living in Thailand, you will be taxed 289,283 บาท. That means that your net pay will be 1,380,849 บาท per year, or 115,071 บาท per month. Your average tax rate is 17.3% and your marginal tax rate is 25.0%. This marginal tax rate means that your immediate additional income will be taxed at this rate. For instance, an increase of 100 บาท in your salary will be taxed 25 บาท, hence, your net pay will only increase by 75 บาท.
Bonus Example
A 1,000 บาท bonus will generate an extra 750 บาท of net incomes. A 5,000 บาท bonus will generate an extra 3,750 บาท of net incomes.