How to configure in lex(integrated with Slack) that able to respond in slack threads?

I have created a chatbot using AWS Lex and I have integrated it with slack and they respond to the mentions in channels(control via lambda).

Currently, the bot responds as a new message however I want it to respond in the slack thread of the original message posted by the user. Does anyone have any idea on how to solve this? Really appreciate your help, thanks.