Text to speech (tts) on demand

I'm very dyslexic and love the text to speech feature but am frustrated that it's only available when a new message comes in. Having tts is night and day for dyslexics.
id like a button to reread a post on the right next to the options button.
It would make it much easier to read back through old conversations or catch up on chat while iv been gone without having to use 3rd party programs, and since tts is already an option I feel this would be an easy win for dyslexics like me.

Please consider this as a feature.