Does Buy and Hold strategy still works ?

It depends. In this NGAS case, apparently it does not. If one holds from 2016 to 2018 last year, they would have made a whopping 200+ % returns, 10 x more than current S&P 500 returns.

However, if one forgets to sell or think price goes up forever , then they would be sorely disappointed as shown on the chart with its waterfall sharp drop!

Lesson learnt : What works for one product (eg. S&P 500 index) may not necessarily apply to other product (eg. NGAS in this case) and to me, that makes charting interesting.

Comment:

half a year later, we can now see that the price has revisit the 1.639 price level when it was last there on 29 Feb 2016.

Let's monitor this over the next few weeks to see if there is any reversal. The downside is pretty limited for now and the likely route to go is UP.