Thai people do not openly discuss things about The Royal family among foreigners with many reasons... so I'll try to squeeze what I have observed. Only westernized Thais would give us better insights.
The King has been very productive especially in the early years. There are numerous footages (old films) you'll see where their King has gone in the rural areas for development. His statements are very careful and serves to inspire the Thais.
Charisma. Even I feels like wearing shirts with "I love the King" here...
He's intelligent, and creative. I believe he has contributed alot in the progress of Thailand from the past century. As far as i remember, he even designed a boat good for Thai rivers (he crafted it himself).
Now, even the gov't is chaotic (a stronger reason to love their King), their monarchy stands strong and silent. It's been like an imaginary scaffolding which preventsThailand from sudden disastrous sinking.
... and look at his face- you'll see it in his eyes.
reigning for many decades, pretty numerous to say why, but when I watch his 60th anniversary last June - like other foreigners, we were all touched, while most Thais cried with tears.