Korea - Transit at ICN

My parents are flying Asiana to ICN and transiting to Thai Airways to TPE (in business class). How difficult of a transfer is this? They only have 1.5 hours.. any specific tips?

thanks
FDW

Very easy transfer: your parents will go through a security checkpoint where they will be asked to show their TG boarding pass (if not available, an e-ticket printout for the connecting flight is sufficient, in which case they should get their TG BP at a transfer counter past security), then enter the departure level of the main terminal (which serves KE and OZ only). From there, they will take the shuttle train to the satellite building (which serves all foreign airlines), where they will have access to the Asiana business class lounge. IIRC that lounge does have showers.

The whole process should take ~15 minutes barring unusual queues.