Update
Reactivating this old thread with a query about transiting Changi next month. which hopefully someone will have more recent experience than I have! We arrive from Melbourne on a Qantas flight at 17.45 and depart on Bangkok Airways flight at 20.10 on separate tickets (both terminal 1). Is this timing a bit tight if we have to go through immigration, collect baggage and check in again? I doubt if Qantas will check our bags through but reading the thread is it possible to go to a transfer desk airside at Changi to check in for Koh Samui flight and get them to arrange transfer of bags onto Bangkok Airways flight?