They've bought 8.5m ATK's and use them in Phuket already. Don't see why they can't use them in CM...
And if students are infected and test positive then there is no difference with family and friends. They are just as positive if they don't take the test.
But vaccination can be delayed as it's of no use to them now, and testing their direct contacts will show who else is positive.
That's how you take care of the situation instead of unknowingly closing your eyes and humming.
Your missing the point that your either entering on a valid Visa which does not require a re-entry permit, or an extension of your permission of stay, which is a 'permit' not a Visa, which requires a re-entry permit.
Assuming you entered Thailand on a Non Imm O single entry Visa, that was 'used' the minute you entered, but you were granted permission of stay for 90 days, which you then continue to extend year by year.
Your question I'm sure is 'if I re-enter on an extension of stay with a re-entry permit'. If your permission of stay expires in less than 30 days on re-entry, then you only require Covid Insurance for 30 days.
If for example you had an extension valid until March 2022 and exited then re-entered on a re-entry permit in October 2021, you'd probably require Covid Insurance for 180 days, or until your renewal extension date in March 2022.