Qr is unlikely keen on pen-lgk revenue. If there is domestic pax, lgk pax may need to clear immigration at pen.
Qatar Airways will serve Langkawi 4/7 from oct 15. as an extension of its Penang service.
Initially served by A330-200 they will switch to B787-800 from oct 27.
QR866 DOH0155 1420PEN1540 1620LGK 788 x13
QR867 LGK1825 1905PEN2025 2330DOH 788 x13
I don´t know if they have traffic rights for the PEN-LGK sector. So, not sure if one can book it - I have doubts because it is a domestic sector wholly within Malaysia ...
If these sectors are operate by mab, almost certain would become a triangular route.