I'm actually sort of contemplating that now, just to avoid the hassle. But I actually booked the bus ride from Bangkok to Siem Reap, it's not that horrible (watched a very detailed YouTube video of a recent transit), and was only $47. The plane ticket on Air Asia is $151. This for the day after Christmas.
you mentioned that when booking one of the Onward tickets it's "reserving for a couple of days", is that sort of like a 'time slot' that expires within a certain timeframe after the purchase? I've never done one of these before.
I was actually looking for 'proof of departure' from Thailand. The kind that may be asked for by the air carrier coming from the United States to Thailand, or by the customs and immigration people at the BKK airport.
people who have never traveled To Thailand, people who don't know the customs and immigration procedures, and people who don't know if there are specific rules for foreigners traveling in Thailand, don't know what's "routine".
just out of curiosity, and by your calculations, if I am arriving on October 29 at 5 AM what would be your estimate of the expected departure date if I do not apply for an extension?