basically it is just Vientiane and Savannakhet that got strict on visa applicaions. I frequently look at the online system of KL and you can even get slots for the same day. Looks like they are very reasonable.
Benjamin Hays on that I have to correct, Cambodia Airport not allow same day OUT/IN. They request 24 hours in country. At land border they ask a small service fee to forget that requirement.
only the land border count will reset on 1.1.2020. They write manually
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or this year
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. No rule re Tourist, when the Thai Embassy in Vientiane changed that "Lady" was heard shouting "ONE PER YEAR", but this is no rule. Without a remark you could apply for a second within same year, but if they approve is a different story.
there are always ways to beat the system. If you in UK try to get a SETV or METV. If you have a past history avoid entry via airport, extend. Than do 2 border run in one year. Take a look at the calendar, we already in September, if you plan ahead you can stay at least 8 -14 month without worry.
do a border run to nearest border, more easy than to fly. If you leave 11th and come back on 11th than you get 10th October. If you come back 12th you will get up to 11th October.