With Oman Air via Muscat in business class to Bangkok or Sri Lanka or Kuala Lumpur.
The rules are unclear, this is a tour operator fare, so you need to be with an OTA (follow our links) you can't book with the airline itself.
If you want to book don't wait to long as the fare could be pulled back at any moment.
For the availability it seems that from Muncih the availability is much better, the best days to travel are on a Thursday or a Friday. From Frankfurt try Wednesday as this seems to be the day with the best availability.
This is how Oman Air business class looks like: