easy enough to book flight day before,same day or even at the airport(possibilty of hanging around though)......shouldnt be a problem around that date,sure u will find one of the many airlines free.
pricewise your not gonna save a great deal......airlines like nok,1-2-go and airasia- only really vary between 1750b-2250b.so if your not 100% sure of yer dates i would just leave it.
1 2 go were doing a great deal in march......not sure when it ends ,think it was for a couple of months.........1750b all routes,which includes,HKT,CM,krabi,surathani,udon??.
all can be paid for fixed rate at 7/11...Great....i love 7/11..i never used the 7/11 service,but read about it inflight,still got 1750 deal from agent down to phuket though.
maybe more info on website......
One-Two-Go Airlines.
ill add i did fly out of don muang,no problem for me,but something to take note if yer planning a connecting flight when u arrive i.e international ,suvarnibaumi