I don't see any deadline on the website. But all those going for June assesment and have applied in april or so have got our official notification to go for the assessment at changi village hotel from 13 June to 24 June. But i guess if u haven applied just apply asap and see how..cuz maybe it's a rolling recruitment, meaning u will still be considered at any time so go ahead and apply!
all the best man! Hope u can make it for the June assessment!