lock in period means you cannot settle your loan in full during that period, but you can still park your money to save interest.

generally, most of the banks do not allow you to offset the interest payment during construction period. you can check with your bank on this.

i with other bank semi-flexi, i start to park money before i got the key, my banker told me as long as not pay all the outstanding amount.

Hi, I am applying for the same type of loan from PBB. I had the same question too as you do. After checking with different sources, I can tell you the following:

The bank only chargesyou progressive interest and does not ask for principal payment when the building is still under construction.
So if you want to reduce interest before VP, you could still put extra money into the loan account.  the extra amount you put in will be used to settle the loan amount(Principal). For example if the current loan amount is 100k and you put 10k into the loan acc. Your loan amount will become 90k. However this 10k which cut down the loan amount cannot be taken out again. You cannot take this 10k out and change your loan  to become 100k again . You can only do that after VP