As in all Asian countries, organisational structures tend toward the hierarchical.
Many Singaporean companies originated as family-run businesses and this adds weight to the push for respect for seniority. The CEO of a family business will tend to be the oldest male family member working at the organisation with other senior employees also being family members. (Obviously these family ties and influences are not a factor when dealing with MNCs working out of Singapore.)
Thus, within traditional Singaporean organisations, all key decisions will be made at the very senior levels with those decisions being delegated down the chain of command for implementation. It is not expected that the middle tier will openly disagree with senior management, as this would infer lack of respect. It is, therefore, important to ensure the right level of contact within an organisation if influence is to be brought to bear on the decision-making process. It is also important to ensure that senior people are dealt with by contacts of similar status. Do not insult by sending in more junior, younger staff than are introduced to you.
Outside the traditional, family-run Singaporean organisation, a whole host of structural approaches can be found – especially in the MNC world and Singaporeans have proved particularly adept at adapting to these differing models. It is often advisable to do some in-depth research prior to interfacing with a company in Singapore in order to find out exactly what type of beast you will be dealing with and thus be able to plan your approach accordingly.