if they go dormant, then that would be the time to do all the digging. In late winter, or the end of the dry season you could take a shovel and dig it out getting as much of the roots as you can, but if you dont get all the roots it would be okay because it will grow back once warmer temps (or rain) return. You would have to tie it to keep it up from high wind though until the roots grow back, and I woundnt expect many flowers until they become established in their new spots.
If this is a big tree you would probably need a crane or something to get it out, but if its not too big all you need is alot of will power, or some nice friends or family to help you lift it out.

Good luck (also Im alot newer to plumerias than many people on this fourm so they may be able to help you out more than I can).

Thank you! How about watering the roots when and how much....before one puts them into the ground again ..or even before one digs them out?
In Bali is now the the end of the dry season coming so that would be a good time? What about following the moon phase...? Is new moon the best for digging out?

Your welcome!

I think you should give it a nice soaking with water when they are in their new spots, and make sure they dont get too dry.

If your plumerias are dormant now, but will be growing again soon, then now is the best time to transplant.

Also, Ive never planted by moon phases, but people say the best time to be planting things like plumerias is during the new moon phase because the gravitational forces makes plants grow easier.

Good luck!

If i recall, Jim Little's book (available at mauiplumeriagardens.com for about $11) has a section on moving large plumerias. The book is worth owning by any plumie person.