Depending on where you are in S.E Asia, the North East (Monsoon) blows from Nov to April.
I sailed Kuantan (Malaysia) yesterday in a North East breeze.
Check the actual wind stats for June at www.windsurf-vietnam.com
In June, the wind is from the South and lighter than the NE.
6m2 ?..........depends on your weight.
Mui Ne is a great place.