I always worry about the airline not allowing me to check in albeit i only had a sticky situation once (Bali to Manila). I just bought a cheap single ticket Manila to Jeju Island eventhough onwardticket.com solution would be probably just as good. Never been asked by immigration authorities though.
Much β¦much easier to get Non-O in UK through the Thai London Embassy website. At least this was my experience having investigated to obtain it within Thailand initially.