To understand stock margin accounts better.

To understand stock margin accounts better.  The % amount a client on margin can borrow should always be regulated by the central bank. (CB) , not the brokers.

If a stock mkt. is very bearish, the CB may decide to increase the %, one can borrow on duly approved listed shares.  For example, a 10 mill. Baht port. of qualified securities, may borrow say a max. 70% of its mkt value, in normal times.  But, if a stock market is overheated, the CB can/should lower the % one can borrow, to say 50%, or anywhere in between.  This max. %, of borrowed money to buy more securities, should always be determined by the CB, never by a broker!  

In the long and recent past there is lots of history here -of this going amiss; only so as these margin-maintenance rules were not strictly followed! 

Daily, so called "mark-to-market" is critical -as are margin-calls and if not met, for any reason (!), (this so by depositing new cash or more margin-able securities), a "force sell" must be executed. This Even so if the client cannot be contacted, or does not respond.

Until this/the above is well understood & adhered by Thai regulators & brokers, margin-buying here will remain a real contentious issue and may even in time bankrupt some brokers? As already happened in the 1970's here -and then, yet again, in the late 1998's., just post the horrific Asian Financial crisis.  

So they, the brokers & regulators and CB (i.e. BOT),  should ask themselves: do you really want to go through all that again.  Deja vu all over again.