To my personal opinion leads the parliamentary democracy to a fascism of a worse or even worst sort.
Political parties are designed to fight for power in the illusion that by this the best politics would be the result. Actually the result is endless greed of power of this parties. Through the endless fights of parties for power they get perfect in doing this, that perfect that many people can no more recognize the real aims which lead parties. The get that perfect organized and perfect in control of society that a legal way against them will hardly be possible. An illegal won't be possible as well, as controlling of citizens achieves new levels so that revolution can hardly take place.
I amnot sure if this system does not reproduce old power structures and just looks different. It seems to be suitable to serve this purpose.
It looks like the parliamentary democracy leads to the despotism.

That is why I advise against parliamentary democracy. Democracy has to be defined new.I have no really well developed alternative to the current system just some points.
For Thailand this means, a team should be set up by the military and the supreme court to select suitable people for every government post. Belonging to a party should be no point.
What skills these people should have you probably know I want to remind that integrity is an important point, if you get negligent in this you may up with a mafia style government after some time, which hides brilliantly behind lies so that many people not even will recognize this. they only get to feel the consequences and the powerlessness because you don't know what to do about it.

Upholding Thai culture as it was and develop it accordingly to it in the face of technology and globalisation is a decisive point what these people should be willing to do. They should not allow that a foreign system is pressed in the country as this is already is happening.
I think it is important to set up a committee to develop Thailand's own independent political economy. You do not need a lot of scientists for this. Experienced and successful entrepreneurs, good Buddhist monks and others of society can help doing that, but it will take time and and needs developing after this. If you do this you have the chance to develop an economy which is fits in Thai culture. If not economy will destroy your culture. Greed is built up in capitalism longing and wishes are induced systematically. to fullfil the wishes for that you have to work hard. Products are often kept imperfect to keep people longing. A whole branch of psychology is behind advertising to stimulate the mentioned above. If you do the work and define your culture and get ready to defend it to recognize intruders and eliminate them or decide to accept this or that change you can keep a lot of chit which is sold as great out of your country.
When it comes to democracy I think when the leaders are bound to strive for harmony and to listen seriously to the people (or find themselves in trouble) you may have more from that than from some elections after which the winner just presses through his agenda. That does not replace elections but I see the necessity to review this point as I recognize there quite some problems which seriously question elections in the common form as a functioning tool of democracy.