If I have an International Driver's License, will that negate the road test at the office when I go to get a Thai license, or will I still have to take a driving test?

A international license is only valid if accompanied by the original license aswell so if you have that then you will be fine, but if you only have a international license and nothing else then i doubt they will allow that but its worth a try

In fact there is no such thing as an international drivers license, its an international drivers permit, and is mearly a "legalised" translation of your own DL.

If an IDP is not presented with your original valid DL, technically the IDP is not valid, as its not a license

To answer the other half of the OP's question, many moons ago I didn't have to sit the driving test, only the colour blind, and reaction tests.

Apparently you have to now do a written, tick the answer type test on traffic signs too, maybe someone else who has recently done a Thai license could confirm?

I did my Thai licence about 8 months ago and showed my international licence and a work visa, also only did the eye test.