The calculations were as follows
Declared 454,575
Deductible expenses 100,000
Total 354,575
Thai bank interest 4,542
Total 359,117
Then 2×60,000 deductible for personal allowance for wife and I.
Total 239,117
First 150,000 tax exempt
Total 89,117
Tax bracket 5%.
5% of 89,117 = 4,455 to be paid
Subtract 681 for withholding tax paid
Total 3,774 tax to be paid.