There are quite a few CrossFit gyms in Singapore (which is interesting, given this is such a small island)….My sig other was pretty tied in to the CrossFit community in Singapore (he was also one of the official photographers for the Asia Regionals as well as for local competitions). Here's what he shared with me:
CrossFit Hub is the box that has been most consistently sending teams to the Asia Regionals and other competitions. That being said, a few new boxes have sprung up, so depending on where you live, one of these might be a good idea. I think it really depends on what you're looking for and where you live, but these newer boxes have better facilities and some great trainers.
If you have any more specific questions, I can try to get some answers for you.
Happy WODing!!