If these smaller 'jewels' are so cheap why aren't the smart global institutions buying them?

Because institutions have strict mandates (rules) which prohibit them to invest in any stock, unless they its shares trade US$ 1-3 million per day. This often means if a Thai stock does not trade 1-3 million US$ per day, it's not even considered. This is an enormous restriction in an emerging market like Thailand and so virtually creates a "hand-cuff" enviroment on the best values. Hence most institutions do not own the true values in SE Asia stock markets. I have often called this "behavioral mispricings".