There is significant irresolution in many countries concerning the design of student loan schemes. In no country recently has there been more uncertainty as to the form that loans should take than Thailand. The Student Loans Fund (SLF), a conventional approach to financing, was introduced in 1996, discontinued at the end of 2005, and re-introduced in 2007. In its place an income contingent loan (ICL) was implemented for one year only, 2006. As part of this debate we contribute to an understanding of the repayment burdens associated with the SLF in Chapman, Lounkaew, Polsiri, Sarachitti and Sitthipongpanich (in this issue).There are important issues with all ICL, and in this paper we consider the critical matter of interest rate subsidies. These are calculated for four different possible ICL arrangements for Thailand: the Thai Income Contingent and Allowance Loan (TICAL), a variant of TICAL, and two alternatives. With a broad-brush approach the subsidies for TICAL-type arrangements and for current debt levels turn out to be between 25 and 40 per cent, but are about zero for our suggested alternative ICLs.Using a better, more disaggregated, approach, subsidies for TICAL-type schemes are estimated to be about 30-55, and 3 and 18 per cent for our alternative ICLs. But with very large debts, the subsidies of all schemes are very high, implying that ICL are likely to be expensive until Thai graduate incomes rise. Importantly for equity however, the interest rate subsidies are delivered to graduates with relatively low lifetime incomes.