1. This post and information might be outdated, some policies might be changed already. I HEARD of that Cambodia government announced that they will not need any PCR tests and vaccinated proof and insurance from 1st April, not at all. Board will be open just as same as before the Covid. I mean I heard it. You must find out by yourself if you need.
2. If you hold Chinese passport and apply Thai Tourist Visa in Thai Embassy in Cambodia, you must wait at least one month, this is FOR SURE. Waiting for one month, this is only for Chinese passport and Taiwan passport.
3. Please don't message me and ask me which flights can be freely cancel, the policy of flights are always changeable due to date and class and some other situations, you must check online and find out by yourself if need. My flight could be cancelled one month ago but it doesn't mean the same flight can be cancelled tomorrow.
You need the insurance which covers Covid, and coverage period is as long as how long you get stay in Thailand due to visa, if you get 60 days visa then coverage period should be 60 days at least.