Assuming I have decided on the condo I want to buy, how much time should I budget for the whole process? I will be using a lawyer.

One agent said the whole process should take no more than a few days but I read somewhere online that,for example, the juristic person has 15 days to provide the certificate that indicates if there are outstanding fees owing on the property. Then there is the title search, bank transfers etc. etc. I'm sure each deal is different but in general how long should I budget in terms of time?

Like you said every deal is different. Mine took a couple months because owner was out of country and he did not trust anyone in Thailand to give power of attorney. Upon owners return we closed the same week.

Once the seller has the Condo's certificate and you have the funds and bank letter you can do change of ownership at the land office in less than 2 hours.

If you have cash and agree the contract in theory it can be done within 24hrs.

In reality you will, I think, want time to look at a contract, check ownership etc.

Don't rush it or you may be sorry and even though you will use a lawyer they'll forget you as soon as the transfer is done. They'll have their fee and if any issues with damage etc etc you'll be on your own.