It is doable, but will be tough.
Don't forget that you need to pay tax and MPF out of your salary. With that and the money you give your family, you will only have about 25k to live on.
Rent and bills would be around 10k, provided you live over on the Kowloon side. You may be able to find a room in a share flat for your budget in the suburbs you listed on the island but it will be harder. The smaller and cheaper apartments don't really have a kitchen, so cooking might not be an option. If you enjoy Chinese food, there are plenty of local food options which are quite cheap and you could feed yourself for 15k a month easily. I have not included the costs for transport as that will depend on where you work.
Not sure what your lifestyle is like where you are right now, but I would definitely weigh it up with a move in HK.