Thai Legal Default Interest Calculator (5%)

Calculate default interest under the Civil and Commercial Code as amended in 2021, at 5% a year, or the 3% statutory rate when no rate was agreed, as simple interest by days.

Under the Civil and Commercial Code amendments effective 11 April 2021, section 7 sets 3% a year where no rate was agreed, and section 224 sets default interest at the section 7 rate plus 2% a year, 5% in total. For instalment debts, default interest runs only on the principal of defaulted instalments. The tool uses simple interest = principal × rate × days ÷ 365.

Example: THB 100,000 overdue for 365 days at 5% is THB 5,000 of interest; 73 days is THB 1,000. At the 3% statutory rate for a year it is THB 3,000.

Where a contract or specific law sets another lawful rate, or a court orders otherwise, use that instead. Section 7 has the Ministry of Finance review the rate every three years, changeable by royal decree, so check the latest decree before using this in a claim or demand letter. This is not legal advice.