If you've let your instrument rating lapse for more than two years you'll need to write the INRAT exam again. Unless. ...... If your other license is recognized by ICAO, you will get an exemption from the exam if you can prove you've done an instrument ride for your foreign license within the past twelve months. For proof of this I think they want a copy of the examiner's marksheet from your last ride. If you can provide that they'll exempt you from the exam, but you'll still have to do a Group 1 Instrument ride when you come home.
I came back to Canada from the UK and this is what I did. I just asked the training department at my old airline for a copy of the paperwork from my last instrument ride. They were happy to oblige. Hope this helps and good luck.
Spenda