Abstract, Preamble, Acknowledgements and Introduction all in Thesis, how to order them? This might be a bit of a complex situation (to explain), so bear with me:

For my Bachelor degree, I am currently carrying out a nature management project. A nature management project normally consists of a management plan but can include other results as well.

As you might have guessed, this is the case for my project. Next to the management plan, I also write a guide and I develop a database. I do this to enable the organization I do this project for to become more autonomous in setting up management plans adapted to their situation and provide a step by step guide to replicate it.

However, my thesis should include all these results. I already decided to put the guide in the Annex. However, the introduction to the thesis is now different than the introduction for the management plan part. That's why I decided to call the introduction to the thesis the preamble, which explains the situation in detail. 

-Is this a good idea? Any suggestions?

The abstract is required to be above everything else, so that stays just where it is. And the explanation I put in my Preamble is too long to put in the abstract, because it can be regarded as a introduction to the thesis instead of just the management plan. 

I must also include acknowledgements. And I just don't know where to place them.

-Between the Abstract and the Preamble?
-Between the Preamble and the Inroduction?
-Or should I just do the acknowledgements after the references?
(I expect people will tell you to consult with your advisor, and you should, but on the other hand I think most of this question does have a right answer, so I've tried to give it.)

It sounds like you have three main parts to your thesis: the management plan, the guide, and the database. So your thesis should have three main sections (if one of the three is an appendix, that's okay), and there needs to be a single introduction that ties together the entire document. One of the things this introduction should do is explain the organization of the rest of the thesis.

If you want to write a more specific introduction to one of the sections, it should go at the beginning of that section. You can call it "Introduction to Section 2" or whatever. Using the word Preamble confuses the issue, and it also sounds pretentious.