There are lots of great birds to see in Thailand but one of the best, to me, is the Great Hornbill. Whilst it is not the rarest bird, it is certainly one of the most memorable and any sighting is a highlight in my book: a few years ago I did a survey and Great Hornbill was voted the third most wanted bird by birders visiting Thailand.
Great Hornbills are striking looking birds but when you hear them flying over the forest canopy the sound is amazing. I have had people ask me in the past if a helicopter is over head; the surprise on their faces when I tell them it is a Great Hornbill is quite funny.
I see Great Hornbills virtually every time I go to Kaeng Krachan or Khao Yai national parks, but it is one of those birds I never tire of seeing and every time it is one of the highlights of the trip for me.