The progressive party that got the most votes in the Thai election has been blocked from governing, and its supporters (including most of the young people) are angry.

It is normal in a parliamentary system that forming a government requires support from a majority of parliament. It is normal, though unusual, that the party with the most seats is blocked from forming a government by a coalition of other parties.

What is not normal about the Thai system is that parliament includes members who were not elected — rather, appointed by the army. The closest thing to this that I know of is the UK's House of Lords.