Me thinks most of your Qs are answered too in therelevant section of thai's website. the following from memeory:
a. yes of course,but officially OLY after youve qualified again at TGm, often airlines will take over existing status of good custmers, but Ill guess youll have to contact the local representative for this
b. depends on the actual arline and if indeed youre booked in y or say ,L,M,. V, etc. TG itself always gives 100% ms on any PUBLISHED eco-fare
c. depends; either 50k in 1 yr(either 1 out of the 2), or 80k over 2 yrs, the same as you need to qualify for gold
d. when youre a member, you get a nice booklet with all the miles, basically there is a lower scale for TG ONLY and a higher one (higher as KF, but I think lower as SQ wants for any STAR for Any STAR**), TG itself goes by nr of miles used up.
e. if you decide to change over: welcome in the ROP-club, but dont expect the same fast service as SQ, however, the actual service is often much more courteous and out-of-the-way (I had both cards/schemes till recently, so can vouch a little)