I noticed the crematorium being constructed on Sanam Luang while passing by on Tuesday this week.

It might safe to assume that the Grand Palace/Wat Phra Kaew may be closed one or more of those days: April 8 - 10?

Songkhran is April 13, 14 & 15 traditionally here in Thailand.

http://thailand.prd.go.th/view_inside.php?id=6137