As far as I know , there isn't a way to use the standard dropdown option in your custom thread list. (Because the dropdown actions are tied to the each message id of the thread) . Here are a few work arounds that I can think of ,
1. Include the standard message list , hide it and clone and place the options for each message. Then you would have to manipulate the links of the option a tag , with your message id and check if the desired action takes place. As we are doing the whole thing as custom , it might be better if you could choose the options that are required and hide the rest.
2. What we usually do , is use the standard thread page - because of its in built functionality and context setting .But we have done extensive customization to change the look and feel and add/remove other stats , custom components for each message using jQuery.
3. Choose the features that you would need from dropdown , and create your own custom components to perform the actions , using REST api.
I am not sure , which one of these would suit your requirement . But I hope one of it helps.
Thanks,
Sam