Yes, in our Singapore system, as well as the US, since its
modelled from there mixed.
There is ONLY one professor in that field in a university. That
professor is supposed to be the best in that field and will chart
and provide research direction for the university in that field of
research. This title is bestowed upon him and is certified as a
permanent tenure. 
Normally, for the same field, there will be 2 to 3 associate
professors who will aid the Professor in that field. These
positions can/may be earned through seniority, no. of publications,
depth of knowledge, appraisals, universal acknowledgement of his
work, etc. They may or may not be permanent tenure positions, but
most definitely are. 
The rest are asst. professors, followed by Dr. (acad), research
fellows.....these are Ph.Ds, but are younger, most prob. about
Next, are Research associates, research assistants, Research
scholars, etc... who do NOT yet hold a Ph.D. but are unable some
abled professors or assc. professor so as to obtain a Ph.D.
Associates,
Assistants meant that they are not yet able to perform independent
research to their potential and write up research journals etc, so
the Assoc or Prof is their supervisors.
Other exceptional positions in academia are Honorary Professor,
Temasek Professor, Visiting Professor, and Emeritus
Professor.
Honorary - a doctor through years of experience in the industry
>30years !! ...therefore university decides to award him/her in
a ceremony...could also be contribution in a world accident, found
a world cure, give money to charity etc. 
Temasek - currently in Singapore there is only 3 such professors,
SUPPOSED TO Chart direct for Singapore in terms of research field,
to make singapore competitive and earn money for Singapore! T.Profs
control/is in charge of Professors in both NUS/NTU! 
Dun even to ask about
their salaries.
Visiting - On sabatical to another University, and is
teaching/doing research for 6months to 1 year.
Emeritus - Already retired, given the supreme honorary title due to
contribution in the arena. And provide consultation and suggestions
to Professors and Assoc. Professors!
There is a sub position called Senior Lecturer....these may/may Not
be professors, their could have a Masters degree, basic degree,
double-masters, who have been teaching in a university for >5
years. They may subsequently be given a scholarship overseas to get
their Ph.D. and then come back as a Doctor or Asst. Prof. in the
future. These are common 5-10 years back as some cannot get the
money to study or go overseas, so their stayed back in univ. to
teach and earn money etc.
