It was reported that Perak State Legislative Assembly held its emergency meeting under a tree(The Malaysian Insider), at a car park (Malaysiakini). Is that lawful?
By convention and under normal circumstances, legislative assembly meeting should be held in the assembly building.
However, if that is not expressly provided either by the Constitution or the Standing Order, the meeting may be held at any place. That must has been the intention of the legislature for not fixing a designated place of the meeting.
More importantly, Parliament or Legislative Assembly is all about the assembly of the people's representives to make laws, not the place they meet.
Therefore, my humble opinion is that a meeting of the legislative assembly held either under a tree or at a car park is lawful.