Household debt rose to 80.1% of the country's GDP in the third quarter of 2013, boosted mainly by the government's tax refund scheme for first-time car buyers.
"This is not worrisome, as people may seek more loans when the economy is poor. A marginal run-up in debt is normal amid an economic slowdown," said Bank of Thailand spokeswoman Roong Mallikamas.
She said lenders are being more prudent in extending loans, while debtors are more cautious in accumulating debt.
At the end of last year's second quarter, the country's household debt accounted for 79.2% of GDP. Thailand is among the highest countries in Asia for public debt but still behind South Korea and Malaysia.
Ms Roong said while the central bank does not want to see higher unsecured loans including credit cards and personal loans, their growth rate is not significant and is slowing to 10% from 30% in recent years.
Commercial banks' non-performing loans (NPLs) at the end of November rose slightly to 2.3% of outstanding loans from 2.2% in October, propelled largely by auto loans.
Auto loan NPLs rose to 1.9% of total auto loans in November from 1.8% the previous month.