Have been told that the 11th & 12th of June are likely to be a holiday, something to do with His Majesty, is that right?

it seems like that

12-13th June 06 are holidays celebrations for the sixtieth anniversary of the accession of His Majesty King Bhumibol Adulyadej .

As for school holidays, it's a safe bet that at least one day will not have classes, but you'd have to ask your administration, which may not know until the last moment, exactly.

Also the 9th of June many offices will be closed and government agencies starting the celebrations.

Don't forget your yellow shirt on the 9th June.