Hmmm...
I don't know why it would die back like that.
I used to have mine in a 2-gallon pot and would forget to water it months on end and still managed not to kill it.
I finally planted it in the ground last year.
It is doing well. However, some new leaves are all "deformed" (all curled up - don't know why either).
Also, it does not put out any flowers anymore (it used too and they smell heavenly).

Are you a Thai-food cook? They are great in Thai curry.