That is the biggest mistake that investors make: that they are afraid!
But look at this: you bought a fund for 1000 units at 100k Thai Baht when SET was 1600. It is now worth 80k. So if you buy now for 160k for example you'd have 3000 units for 260k Baht. If the SET goes up just 10% from now (to about 1550) you will have 286k Baht, and a profit of 26k.
But when you do nothing, you simply lose 20k as your 100k fund is now worth only 80k.
So if you believe in the future in country, help to make it better!