My son's interested in dance too, so I've looked into this quite a bit. There are a LOT of girls ballet classes in Singapore but few options for boys. Here are a couple you might try:
1. Beat street studio -
http://www.beatstreet.sg/
I took my son to visit the studio about six months ago when he wasn't quite ready to go on his own yet. But I met the owner/instructor Jose and had a good impression, so I expect to try his Saturday morning Acro hiphop class. They have other kids classes as well.
2. Jitterbugs -
http://www.swingapore.com
They have jazz, tap and hip hop starting age 4.
Note we haven't tried any of these (my son just turned 3) but we intend to next year. If you do try them, I'd love to hear about your experiences.
p.s. Have you considered gym classes? Lots of music, jumping around, even stunts on uneven bars. I wholeheartedly recommend The Little Gym (Forum or Marina Square) - their teachers are just phenomenal with kids. They have university degrees and are really child education professionals who guide kids through experiences of pushing their limits and gaining confidence from self-efficacy.