no, they didn't ask for the cover letter. But I thought it is beneficial to explain about my current situation and the medical appointment as I am continuing treatment from when I spent time in Bangkok earlier this year.
as said above, it is always best to ask the Embassy directly. It wasn't an issue for me as my funds are well over the required minimum and have been so for years.
my statements were from an Australian bank, so in english. I would recommend to just send an email to the Embassy or drop by and ask if you are already in Jakarta. Based on my experience they seem to be very approachable and happy to help.