I want to know how did they board the plane, no test before boarding?

The probably got infected after getting tested.

A test is required for all non Thais to board a flight to here.

Which is quite worrying to me, as I'm catching a plane on 13th, I sincerely wish I don't catch it on board!

Fake certificates is another possibility.  They've been reported in the UK.

2 hours ago, CanadaSam said:

I want to know how did they board the plane, no test before boarding?

t is required to be tested no more than 72 hours befor flight, there is plenty of info about this on Thai Visa

Most 'experts' (whoever they are) believe that the present vaccines will protect against the UK variant, though this does not help if you are already infected. However, a more infectious strain increases the reproduction rate (R) and hence requires a larger fraction of the population to be vaccinated in order in order to get some kind of 'herd immunity' (herd protection is a more apt description), whatever that is. More worrying is the South African strain which reportedly has more substantial differences in its protein makeup. It does not seem to have spread that widely as of now, but at least two cases have been detected in the UK.