Originally Posted by ikura

A quick search on ANA tool (which you should learn to use) revealed this:

Outbound this is available:

BKK-FRA 22JUN dep 12:45 PM arr 19:00 PM on Thai
BKK-MUC 22JUN dep 13:25 PM arr 19:50 PM on Thai
BKK-ZRH 23JUN dep 00:30 AM arr 07:35 AM on Thai

Inbound this is avaiable:

MUC-BKK 06JUL dep 21:50 PM arr 13:40PM+1 on Thai
ZRH-BKK 06JUL dep 13:30 PM arr 05:30AM+1 on Thai

Why would you want to book a separate ticket to TLS? There is a lot of availability to TLS in business class on Lufthansa from Munich/Frankfurt and on Swiss from Zurich as these are hubs of the respective airlines. I would book all the way through to TLS if I were you.

You could easily book something like BKK-ZRH-TLS-MUC-BKK.