I did the exam earlier this year and did study from the PMBOK 5th Edition. The Practice Standard has not yet been updated but it will be very soon as the new edition draft review was completed recently so probably the new edition of the standard will be released the the 1st or 2nd Quarter of 2019 and then exam will change by then.
A number of members have posted extremely valuable advice about their journey to RMP certification on this site which you can search by just typing RMP exam in search bar. However, two sources which help me get through are
- PMI- RMP Exam Prep by Rita Mulcahy
- PMI-RMP Exam Prep by AlKuwaiti Saving Changes...