Hi Lysha,
It could be diabetes - please take your son to the doctor ASAP. If it IS diabetes he needs to get it under control as quickly as possible, and if it's something else that will also need to get treated anyway. Does he need to use the loo a lot? This combined with a strong thirst does suggest diabetes. Please let us know how you get on, and if he does have diabetes you'll both find a huge amount of support here!
Claire x