I think you'll find offices are closed on the fifth because it is Fathers' Day, being the birthday of the recently decease King Rama 9, rather than World Earth Day.
The consulate in Savannakeht and embassy in Vientiene are closed on 4th as it is a substitution for National Lao Day, which is actually tomorrow.
As an aside, Monday 11th December is also a holiday. It is a substitute for Constitution Day which is on Sunday 10th.