I have BCBS Basic so far I've hadn't had to use it in Thailand but they told me if they don't bill the plan direct I have to pay and submit the bill's for reimbursement.
I almost had the same problem cause I didn't realize it's leapyear but I landed 11:20 PM so I just waited until it was passed midnight to go through passport control. Problem solved!
I flew with Korean air out of JFK N.Y. they just asked for my Visa and I showed it to him with no problem. I come here every 3 months and depending on airline some don't even ask. I'm here twice a year for 90 days each time