here is the archived discussion:
http://www.sgforums.com/?action=thread_display&thread_id=58195&page=1
from there u can read up on how to calculate the suffixes.
every vehicle prefix series in singapore will use the same
19-alphabet cycle suffix, just that the first alphabet i.e. SBS1Z
will vary with different prefixes. that said, TIB uses
"ECAYUSPLJGDBZXTRMKH", which means TIB1 is E.
and thus, for every jump from 9 to 10, it will skip 1
alphabet;
for every jump from 99 to 100, it will skip 8 alphabets;
for every jump from 999 to 1000, it will retain the same
alphabet.
tis applies for every series in singapore, be it SBS, TIB, SBT,
SCR, SFS, PA, GV etc.
i regret that the script that can generate the code has been taken
off and it might have been lost forever, but hope someone can come
up with the program to generate the suffixes one day. 