The new number to SMS is no longer 36767.
SMS to 82411633 instead.
The format is still the same (separated by space):
MNC NRIC DestinationCountry DepartureDate (DD/MM/YYYY) ReturnDate YourHPNumber
Notification for NSmen Overseas Trip is only needed if you travel for more than 14 days.
Disclaimer: The above is correct at the time of posting. Please double confirm with the official sources in case there are any updates.
Update 2019: NSmen no longer need to notify Govt of overseas travel under 6 months. Read more at: https://www.todayonline.com/singapore/nsmen-no-longer-need-notify-govt-overseas-travel-under-6-months