To borrow money with the purpose to buy a property in Thailand is in principle impossible if you are a foreigner. This has to do with the regulations laid down by the Bank of Thailand. If you wish to borrow money, the best solution is most likely to do it in your home country — implying both better conditions and a smoother process.
However, there are now some off-shore-like solutions offered by Bangkok Bank and United Overseas Bank (UOB) via Singapore — although being both rather costly and rigid.