As Malaysia's economy develops, it is only natural that it's military improves over time. Each country needs to prioritize its defence spending in accordance with its own needs.
IMHO DavidDCM is only partially correct in his analysis and would like to add to the discussion with my point of view (POV).
1. The point is not to compete with Singapore in the technological rat race (i.e. do not compete on your weakness)
2. The military value of Malaysia's purchase of PT-91M should be measured by its ability to enable the army to develop it's tank doctrine. Let my use 2 other sub-points to explain my POV:
(i) Despite the limitations of PT-91M listed in this forum and elsewhere, it is still a MBT. Numbers purchased may be small, but the value the army will derive from it will be huge. Once you have a MBT and you can plan modern armour ops. This also means you can also more effectively plan against MBT Ops against your forces. Therefore the PT-91M provides ops flexibility for the Malaysian Army.
(ii) It also forces the other side to take its presence into consideration in the battlefield. The opponent cannot move without proper amour support and will make the opponent's range of tactical responses more predictable.
3. This means that the opponent has to spend even more just to take this into account. It you look at SAF's website, you will find that they are considering combined armour "swarming attacks" and even "thunder runs" to further develop their amour doctrine. For more details see:
www.mindef.gov.sg/imindef/publications/pointer/supplements/LDAC.html
For the reasons above, the purchase of the PT-91M is worth it's weight in gold.