Find out the water temps at depth where you will be diving. Then go to your local dive store and discuss your trip with them. A reputable dive shop will be able to fit you with either a full wet suit or shorty that should do the trick. They will consider your body type and size, experience level and budget to help you make the right choice. Comfortable diving should be a priority, so please depend on your local dive shop rather than just buying blindly online. (And for the record, no, I do not own a dive store, nor does anyone in my family. I just strongly believe that building a good reputation with your local dive shop is crucial for avoiding expensive mistakes in equipment purchases.)
For most tropical diving, you will be looking at a 2-3 mm wetsuit or combo (2mm arms/legs with 3mm body). If the temp at depth is very warm (in the 80s F) you can get away with a shorty.
Otherwise for an extended stay with multiple dives, you should consider a full wetsuit, remembering that the more and more often your skin and body are exposed to the water unprotected, the more heat you are giving up to the ocean. Over several days of diving, that heat drain can be of concern depending on your comfort level and what kind of shape/health you are in.
Again, a reputable local dive shop can answer these questions for you and steer you in the right direction. One last thing: if you are looking for a decent wetsuit at a decent price, consider the Tilos brand. My wife and I are very satisfied with ours.
Hope this helps.
UomoScuba