How much does cleaning of jacuzzi cost per month in Phuket, minimum and max?

I would guess around 1,500 THB/month, can that be correct?

Can I do it myself, and if so, what do I need to buy and how much time would I need to spend each week?

I've decided to rent an apartment with a jacuzzi in the bathroom, and the landlord agreed to lower the rent but added I need to take care myself of the cleaning of the jacuzzi. Have never done that before, can I do it myself easily and lower the cost compared to letting some professional do it for me?

Well I have never heard of such a thing as "cleaning the jacuzzi". Of course you have to clean it after you use it, but nothing else. Mine has never been cleaned besides the obvious cleaning as if it was a regular tube. The only problem you may have is if the water is hard you may get limescale clogging the pipes, maybe he talks about that... to prevent it is easy, just use a good filter for the water (and another one for the drinking one).

"How much does cleaning of jacuzzi cost per month in Phuket?"

One of those questions that you can honestly say has never crossed your mind before.