I managed two back to back with different schools. If you are progressing through a course some are meant to be upto 3 years (though might depend on the schools relationship with immigration).
The issue i had was immigration at BKK if you have to leave and come back. Having all the paperwork and a legit visa still wont be enough to just be allowed thru.
They weighed my bag at the gate and saw that they sent someone back to check theirs in. I had a medium sized back pack so nothing that looked overly heavy. Might have been that particular flight tho.