I think I have the same want as you, Aizada:
I’d love to be able to have a Telegram group chat, with topics enabled (that somewhat correspond to the categories on Discourse), and then, in the Discourse/Chat integration settings, specify which topic it should post to.
I’ve tried to create a group chat with topics now (with just the bot and me), but when I type /help within a topic, the bot answers in the general chat.
Have you looked into this @david? I found this Stack Overflow thread, that shows how to get the message_thread_id (which is the topic id) and says that the bot API got support for this in 6.3.
Thanks for your work anyway! 