I'm planning on getting a single entry 'ED' visa quite soon and extending it every 90 days over the next year or so.

With my first 90 day stay on the visa, I have to leave the country after about 6 weeks.

I'm just wanting know, do I go ahead and get a re-entry permit or is there any issues about getting re-entry permits during the first 90 day stay (before any extensions are made)?

Just double checking as I would hate for my visa and permit to stay to be cancelled.

Any clarification would be greatly appreciated.

Cheers

A re-entry permit is only valid for the current permitted to stay period so unless you make a trip during that first 90 days it will expire unused. So yes if leaving within 6 weeks and returning prior to 90 days you can obtain any time before departure.

if you have an ED visa and want to leave the country for any reason what are the requirements on re entry -do you need to do the whole thing again et?

If on an extension or want to extend you would need a re-entry permit prior to travel. If just using a multi entry visa you just enter for a new 90 day stay using the valid visa.