Why can't they check through your bags? They should be able to pull up your second reservation and check through your bags from TPE (I assume). You will not be able to checkin for the OS flight probably although OLCI should work. Do stop at the C/I counter in BKK to have your bagage tag entered in the OS system. If it works of course.

If not, IIRC OS have their own C/I desks and these will probably open three hours before departure.