Summary
If you make 30,378,396 บาท a year living in Thailand, you will be taxed 10,153,289 บาท. That means that your net pay will be 20,225,107 บาท per year, or 1,685,426 บาท per month. Your average tax rate is 33.4% and your marginal tax rate is 35.0%. 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 35 บาท, hence, your net pay will only increase by 65 บาท.
Bonus Example
A 1,000 บาท bonus will generate an extra 650 บาท of net incomes. A 5,000 บาท bonus will generate an extra 3,250 บาท of net incomes.