trademark for product strategy

I can't advise you as to Hong Kong law but in the US, you would open yourself up to an opposition to your proposed registration from your direct competitor with the possibility of your mark being denied registration protection. The standard is "likelihood of confusion." A lot will depend on how vigilant/aggressive your competitor is about policing their IP. Factors that might mitigate against the likehood of confusion would be if the presentation of your logo (e.g., colors, font, design, trade dress if any, look and feel of your website) was very dissimilar from your competitor's.

Not only would you run the risk of TM infringement, you will probably run into unfair competition, passing off, misrepresentation, and possibly other issues. Be smart - pick another name/brand - do not go looking for trouble with trademark infringement, unfair competition, and other problems.

In addition to what my colleagues said, based upon your fact pattern you could also be liable for WILLFUL trademark infringement which carries a far more severe penalty - treble damages or 3x the amount of actual damages determined by the court - not to mention a possible award to the plaintiff for their attorneys fees in bringing the lawsuit against you. What you are describing is precisely what is outlawed in trademark law and if you get caught, you could face serious consequences that will make you really regret "piggybacking on your competitor's name."