When is the right time to ask for LOR from employer/manager?

Hi guys, I am apply for fall 2023 and the priority deadlines of the colleges are around December 15 and I want to submit application by this deadline . When would be the right time to ask managers/employers for LOR ? Asking this because once I ask them for LOR it becomes very clear that I am thinking of leaving the company...so i want to ask at the right time, not too soon not too late. Thank you #LOR