This happened to me when my Dad died unexpectedly early last year. I'd already booked a return flight to Australia leaving the next week to visit my parents for 3 weeks.
The call came in the afternoon and I was able to book a direct flight leaving the next morning. My wife and I drove through the night from Khon Kaen to Bangkok so I could catch the flight (there were no flights from Khon Kaen that would have allowed me to catch the flight). My 12 month extension was in order and I already had a multi-entry.
That worked out for me, but I made one (expensive) mistake. I didn't cancel my already booked return flight figuring I could use the return flight. When the time came to return I found out it was airline policy to cancel the return if you didn't show up for the initial flight. I ended up booking a new return and had to forfeit the cost of the two way return flight. So the total cost was about $3,700 ($1,600 for the forfeited return flight, plus $1,400 for the new direct flight booked at the last minute, plus $700 for the new return).