What is this "new interest rule" on mortgages?

According to the Nation Thailand, the central bank has changed the way interest is calculated on mortgages.  I can't for the life of me follow what they are trying to say in the May 09 article titled "New interest rule introduced to relieve load on borrowers, cut NPLs":

https://www.nationthailand.com/business/30387535

Can anyone who speaks and understands Thai logic please explain to me in conventional mathematical terms what it is they are trying to say here? What is it they actually changed? An example would be helpful.  Mortgage interest calculations are very simple by nature. There is a principle due. There is an interest rate. You calculate interest based on the outstanding principle using the interest rate. You make a payment, the principle reduces, and the interest goes down. Simple.

What on earth does "if the borrower failed to pay the 25th instalment, the bank would charge interest on both the 25th instalment as well as the remaining 215 instalments".  Only a Thai could possibly make sense of that statement. Why are you paying interest on installments, themselves which are already mostly interest, and which by definition are variable because the interest rate varies???

Bafflled and in need of someone who can translate nonsense...