Silver-breasted Broadbill（ギンムネヒロハシ） The one with white necklace is a female. When I was in Bangkok some years ago, I got the Bangkok Post calendar of Thai birds and this Broadbill was in its August page. So I've been wanted to see it since then.
Two couples were chasing each other just like "A Midsummer Night's Dream"'s Hermia, Lysander, Helena and Demetrius along the forest road. In the rain forest, trees are so tall and dense that it is easier to see birds along the roads than inside of the forest.