Drink drive unless recent will not get a mention and would not affect your ability to get a visa. Driving offences in general are not regarded as criminal offences.
I am surprised bus tickets are accepted, but I guess providede you get out of the country, immigration should be satisfied. Them there is the airline to keep sweet.
I had an option to change flights. It's just that the cost was OTT. All three classes of ticket seemed to have the paid change option. Mine could not be cancelled. In the old days I'd have readily booked a throwaway flight to KL or even Siem Reap, but flights have climbed in price since then. Thanks for your thoughts and advice. There's options to explore.
I just bought a return ticket as the rule changed so I counted on just 30 days rather than pay for a date change. Then the government has 2nd thoughts.
Surely you can supply some proof of booking, whether a screen shot or a credit card statement. I have never been asked to supply proof of a booking but fully understand your point about some nations being asked to show more proof than others.