not sure but only 18 country where in the list and singapore in that list as i saw in WWDC yesterday. maybe when they release full list of what country get the iphone then we will know, as for me i assume its around august or september(last in list of apple iphone released)
18 More Countries Will Get The IPhone 4 In July 2010 Including
1 Australia
2 Austria
3 Belgium
4 Canada
5 Denmark
6 Finland
7 Hong Kong
7 Ireland
8 Italy
9 Luxembourg
10 Netherlands
11 Norway
12 New
13 Zealand
14 Singapore
15 South
16 Korea
17 Spain
18 Sweden

And
19? Switzerland.?

this is not true source i think..

So maybe malaysia will be in august or September.