From what I read in this forum it seems that a rebooking of a RTW ticket could prove to be a rather time consuming task, because the staff who should deal with your request lacks of experience.

I will leave Switzerland beginning November for a RTW; part of the ticket are the legs BKK - RGN - BKK. It may be that we decide to skip Burma because of the current political situation in this country. Do you think it could also be lengthy proceeding if we only want to skip this two legs (i.e. basically do not book any new flight, but only leave away two flights)? Should it be better than before we leave Switzerland (the travel agent will deal without problems with my request) or can I deal with this on any airport without major hassle (and gain the option to decide later)?

Moreover, do you think there is any chance that the rebooking fee could be waived because Burma has become a rather risky destination?

Many thanks!

You should be able to do it anywhere but I'd do it only when plans are known and I have a spare few hours for them to redo.

I'd only expect the rebooking fee to be waived if TG stops flying there (like CX and CMB).