1. The ferry schedule between Lipe and Langkawi as well as to the mainland is the MAIN issue.Ferry from Penang then ferry to Koh Lipe should be possible. I have not checked the timings so at worst it might mean a night in Langkawi.
2. There are two ferry routes from Langkawi(Kuah Jetty) to the mainland ie. Kuala Kedah(closer to Penang) and Kuala Perlis. You need to research the various connection options from these two places to Butterworth.
3. Ferry from Langkawi to Koh Lipe departs from either Kuah or Telaga and they are miles apart(27km).
Malaysia is one hr ahead of Thailand so be careful of the time difference.
Have fun.